A Structure Proof Cholesteryl Quaternary Salts

Citation preview

NORTHWESTERN UNIVERSITY LIBRARY Manuecript Theses

Unpublished theses submitted for the Masterfs and Doctor?s degrees and deposited in the Northwestern University Library are open for inspection, but are to be used only with due regard to the rights of the authors. Biblio­ graphical references may be noted, but passages may be copied only with the permission of the authors, and proper credit must be given in subsequent written or published work. Extensive copying or publication of the thesis in whole or in part requires also the consent of the Dean of the Graduate School of Northwestern University. Theses may be reproduced on microfilm for use in place of the manuscript itself provided the rules listed above are strictly adhered to and the rights of the author are in no way jeopardized. This thesis by . » . . . . . . . . . . has been used by the following persoris, whose signatures attest their accept­ ance of the above restrictions. A Library which borrows this thesis for use by its patrons is expected to secure the signature of each user.

NAME AND ADDRESS

DATE

NORTHWESTERN UNIVERSITY

A Structure Proof of CLolesteryl Quaternary Salts

A DISSERTATION SUBMITTED TO THE GRADUATE SCHOOL IN PARTIAL FULFILLMENT OF THE REQUIREMENTS for the degree DOCTOR OF PHILOSOPHY

DEPARTMENT OF CHEMISTRY

By Melvin Jerome Bigelow

Evanston,

Illinois

August, 1950

P ro Q u e s t N u m b e r: 10060968

All rights reserved INFORMATION TO ALL USERS The q u ality o f this re p ro d u c tio n is d e p e n d e n t u p o n th e quality o f th e c o p y su b m itte d . In th e unlikely e v e n t th a t th e a u th o r did n o t send a c o m p le te m anuscript a n d th e re a re missing p a g e s , th e s e will b e n o te d . Also, if m a te ria l h a d to b e re m o v e d , a n o te will in d ic a te th e d e le tio n .

uest P roQ uest 10060968 Published by P roQ uest LLC (2016). C o p y rig h t o f th e Dissertation is held by th e Author. All rights reserved. This work is p r o te c te d a g a in s t u n a u th o rize d c o p y in g u n d e r Title 17, U nited States C o d e M icroform Edition © P roQ uest LLC. P roQ uest LLC. 789 East E isenhow er Parkw ay P.O. Box 1346 Ann Arbor, Ml 48106 - 1346

ACKNOWLEDGMENTS The author wishes to express his sincere apprecia­ tion or the patience and understanding shown him by Dr. L. Carroll King. Thanks are also due to many other faculty members of the Chemistry Department of Northwestern University for m any helpful suggestions;

in particular,

invaluable

aid was given in the kinetic experiments by Dr. Ralph 0. Pearson and Mr. Stanley Danger.

60X765

TABLE OP CONTENTS INTRODUCTION - --HISTORICAL

-

- - - - - - - -

- _

i

------

4

DISCUSSION 1. A Structure Proof of Cholesteryl Quaternary Salts - - - - - - - - - 1 6 2. The Preparation and Reactions of Epicholesterol and Epicholesteryl £ - Toluenesulfonate - - - - - - - - 2 8 KINETIC CALCULATIONS AND RESULTS - - - - -

37

DISCUSSION OP KINETIC RESULTS

49

--------

EXPE R I M E N T A L Cholesteryl £-Toluenesulfonate (II) - - 51 Cholesterylpyridiniura £-Toluenesulfonate (XXII) - - - - - - - 5 1 CHOlesterylpiperidine (XXIV) - - - - - 51 Cholestanylpiperidine (XXV) - - - - - - 52 Cholestanol - - - - - - - - - - - - - - 5 2 Choiestany1 £-Toluenesulfonate (XXVI) - 54 Epicholestanylpyridinium £-Toluenesulfonate (XXVIII) - - - - - 54 2-Cholestene - - - - - - - - - - - - 55 ^picholestanylpiperldine (XXX): by Hydrogenation - - - - - - 5 5 by Displacement - - - - - - 56 Epicholestanol - - - - - - - - 57 Epicholestanyl £-Toluenesulfonate (X X V 1058 Cholestanylpyridinium £-Toluenesulfonate (XXIX) - - - - - 58 Cholestanylpiperidine (XXXI) by Hydrogenation - - - - - - 58 by Displacement - - - - - - 59 Cholesterylisothiuronium £-Toluenesulfonate (XXIII) - - - - - 60 5-Chole stene - - - - - - - - - -q- - - 50 The Reaction of Cholesteryl £-Toluenesulfonate and piperidine - - 61 Time Study - - - - - - - 53 Hydrogenation of cholesterylpiperidine (B), the Unknown - - - - - - 54 Peroxyphthalic Titrations of Various Amines - - - - - - - - - 65 Attempted Reaction of Cholesteryl Methyl Ether and Piperidine 66 Reaction of Cholesteryl £-Toluenesulfonate and Morpholine - - 66

EX P ERIMENT A L (c o n t fd ) The Synthesis of E p i c holesterol 50C-D±hydroxychol e s t ane - 6 - iso thi uronium £ - Toluenesulfonate - - - - - 67 3ft 5^-Dihydroxycholestane (XLIV) - - 68 3f,5*-Diaeetoxycholestane (XLV) - - - 68 3P“Hydroxy-50f-acetoxycholestane ( X L V I )69 Epicholesterol (VII) - - - - - - - 70 Epicholesteryl £-Toluenesulfonate (XLVIII)

Reaction of Epicholesteryl p-Toluenesulfonate (XLVIII): with pyridine - - - - - 71 with piperidine - - - - 72 w i t h metha n o l - - - - - 74 Hydrogenat i o n of the Pyridinium Sait, p. 71, to Cholestanylpiperidine 72 R o t a t o r y -Dispersion Curves for Two Samples of Cholestadiene (XXXV) 75 Nineties of Reactions of Epicholesteryl £-Toluenesulfonate (XLVIII) 76 SU M M A R Y

-----------

BIBLIOGRAPHY VITA

- - - - - - - - - - -

7Q DA

83

1 INTRODUCTION The year 1932 marked an important milestone in the chemistry of the steroids.

It was in this year that the

present accepted structure of cholesterol posed by Windaus and Wieland,

(I) was pro­

climaxing nearly a century

of endeavor on the part of hundreds of workers.

And in

this same year a German chemist named Walter Stoll ob­ tained a surprising ’'isomeric 11 cholesteryl methyl ether. It was this obscure piece of evidence which opened a minor but interesting field of Investigation to steroid chemists, and the resulting work on the "jL-steroid rearrangement” laid the groundwork for the investigations reported In this thesis. Before a discussion of steroid chemistry is under­ taken,

it is advisable to review briefly the structure

and nomenclature of these compounds. cholesterol

(I) Is given below,

system In general use:

The structure of

along with the numbering

2 It has b een shown^ that the steroid nucleus lies in a relatively flat plane; it is convenient to label sub­ stituents w ith reference to this plane.

The generally

accepted nomenclature is that any group projecting out of the plane of the rings is designated

0 , while a group

projecting back into the plane is O'. Another method of nomenclature designates the natur­ ally occurring epimer f,normalM and the unnatural or syn­ thetic epimer "epiM#f.

This system is somewhat objection­

able in a discussion of general steroid chemistry,

since

the configuration of the naturally occurring isomer must be known to the reader, but will be used to distinguish the epimers at

In this thesis with the understanding

that the "normal 11 configuration is 3 0 and the "epi" con­ figuration is 3of . Since cholesterol (I), however, tive compound,

is an optically ac­

its absolute configuration is unknown—

that is, cholesterol may be represented either by the formula (I) or its mirror image. one fundamental assumption.

It Is necessary to make

The assumption conventionally

made is that the angular methyl group at G 1 0 is In writing structural formulas, the configuration of substituents is shown by using solid lines for ft and bro-? ken lines for Of.

The formulas of three spatial isomers

'“'For a discussion of steroid nomenclature see Fieser and Fieser, "Natural Products Related to Phenanthrene", Third Edition, Reinhold Publishing Company, New York, (1949), pp. vi-viii.

are shown below#

Only the A and B rings of these com­

pounds will be shown,

since the rest of the molecule is

identical with cholesterol

(I).

Only cholesteryl deriv­

atives will be discussed in the text; therefore to save space and time only the A and B rings will be shown in structural formulas throughout the thesis#

N 30-cholestanol (cholestanol)

3Q(*-cholestanol (epicholestanol)

30-coprost anol (coprostanol)

Under certain conditions cholesteryl derivatives can rearrange to form a class of compounds containing a cy­ clopropane ring with a bond between substituent at Cg.

This class of derivatives is known as

the ,,i>-eholesteryl,f series, cholesterol,

and Cg, and a

and is illustrated below by

the parent hydroxy compound of the series.

^-cholesterol The rearrangement of cholesteryl to ^-cholesteryl derivatives is the classical example of the i_-steroid rearrangement, which has since been shown to be a general reaction of all steroids with a 5,6-double bond.

^-hydroxyl group and a

A discussion of the chemistry of these

interesting compounds will now be undertaken.

4 HISTORICAL Windaus and D a l m e r ^ in 1919 are generally consid­ ered to have prepared the first i_-steroid when they de~ hydrohalogenated

30-chlorocholestan- 6 -one to obtain Hiet-

erocholestenone"*

However, these investigators were u n ­

able to prove the structure of their new compound,

and no

attention was given the field until Stoll^® reported the results of an investigation of the preparation of methyl ethers of steroids through their £ - toluenesulfonate es­ ters.

Cholesteryl ]D-toluenesulfonate (II) when refluxed

with methanol gave a levorotatory cholesteryl methyl ether (IV), but the addition of acetate ion changed the course of the reaction and led to the formation of a dex­ trorotatory cholesteryl methyl ether (III), called "icholesteryl methyl ether".

xjj f V Y

OAsZ

= % oh

II

>

?Hs2H-r III

IV

At first it was thought most probable that compound III was epicholesteryl methyl ether

(VIII)^,

and it was

not until 1937 that the investigations of the Princeton group under Wallis actually elucidated its structure. Wallis, Fernholz,

and G-ephart^-*- prepared i^-choles-

teryl acetate (V) from the reaction of cholesteryl toluenesulfonate

jd-

(II) with acetate ion In acetic anhydride

5 and saponified it to give i-cholesterol

(VI), which dif­

fered from all known Isomers of cholesterol*

Ford and

Wallis "*"5 prepared i^-cholesteryl methyl ether (III) by the alkylation of i_-cholesterol (VI), and epicholesteryl methyl ether (VIII) from the alkylation of epicholesterol (VII), and showed these two compounds to be very dif­ ferent in properties.

The reactions used in this work

are shown b e l o w *

^s°

oAo

oH

v

ii

VI

VI

III

VII

VIII

i-Cholesteryl acetate

(V) does not react with per-

benzoic acid or dilute bromine solution; this fact led this group to the structure (III) for ^-cholesteryl derivatives,

and this was later confirmed-^ £>y conversion

of i-cholesterol (VI) to i-cholestanone by hydrolysis to cholestan-30-ol-6-one

(IX), followed (X).

Compound (IX)

6 was also shown by Heilbron*^ to be identical to "heterocholestenone", the compound of unknown structure prepared by W i n d a u s ^ .

OH

o

VI

X

In 1935 Marker*^ and R u z i c k a ^ studied the prepar­ ation of cholesteryl and cholestanyl chlorides.

Prom

cholesterol (I) the same cholesteryl chloride (XI) was obtained with either phosphorus pentachloride or thionyl chloride.

Upon treatment of compound XI with acetate ion

in glacial acetic acid and subsequent hydrolysis, chol­ esterol

(I) was obtained.

With cholestanol

(XII), h o w ­

ever, phosphorus pentachloride gave a- low melting chloride (XV),

and thionyl chloride gave a high melting chloride

(XIII). mer

Epicholestanol

(XIV) gave the high melting iso­

(XIII) with phosphorus pentachloride,

melting isomer (XV) with thionyl chloride.

and the low Hydrogen­

ation of cholesteryl chloride gave the high melting iso­ mer (XIII). The correct stereochemical relationship of these chlorides was first proposed by Bergmann^ and later es­ tablished by S h o p p e e ^ .

The high melting isomeric chlor­

ide (XIII) on treatment with acetate ion in n-valeric acid gave after hydrolysis epicholestanol (XIV), while

7

The Cholesteryl and Cholestanyl Chlorides

S0C1

2, Pt0o h

\r l.OAc

S0C1

= -110°, was identified

22

The Reaction of Cholesteryl ^-Toluenesulfonate and Piperidine

(Identical to XXIV)

Unknown B, m.p. 100

II

C , oil (XXXIII)

D, m.p. 75-7°

(XXXV)

23 as cholestadiene (XXXV)",.

This compound was obtained in

20% yield; it was never very pure. In an effort to determine the structure of the u n ­ known compound (B),

several experiments were tried.

Its

analysis corresponded to a monocholesterylpiperidlne, and when allowed to stand exposed to the air for a few days it softened, turned yellow,

and smelled of piperidine.

This

seemed to indicate that compound B was actually a choles­ terylpiperidine;

also, when purified cholesteryl £-toluene-

sulfonate and carefully purified piperidine were allowed to react, the ratio of products was the same as when the ordinary grade materials were used. To establish the presence of a double bond in the compound, however,

a peroxyphthalic acid titration was essayed; anomalous results were observed.

cholesterylpiperidine

The compounds

(XXIV) and B each used three moles

of peroxyphthalic acid, while an impure sample of i-cholesterylpiperidine

(XXXIII^ used two moles, perhaps for­

tuitously; benzylpiperidine and cholestanylpiperidine each used one mole. conclusive,

(XXV)

While these results seem rather In­

one can at least say that compound B appears

to have double bond, character. The hydrogenation of compound B led to a cholestanylpiperidine

(or coprostanylpiperidine) m.p. 96-7°, which

was at first thought to be epicholestanylpiperidine

(XXX);

*For a discussion of this compound see Fieser and Fieser, "Natural Products Related to Phenanthrene", 3 rd Edition, Reinhold Publishing Co., New York (1949), p. 249.

24 however,

this compound gave a sharp depression in melting

point when mixed with an authentic sample of compound (XXX). A time study of the reaction of cholesteryl jo-toluenesulfonate

(II) and piperidine was undertaken to see w h e ­

ther any of the four compounds

(A, B, C, or D) were ac­

tually intermediates in the reaction, but the ratio of products was the same after four hours

(the reaction was

complete at this time) and after one hundred hours reflux. This information,

summarized in Table 2, shows that :i-

cholesterylpiperidine

(C or XXXIII) is not an intermed­

iate In the formation of cholesterylpiperidine or of the unknown compound B.

(A or XXIV)

Compound (XXXIII) is ac­

tually formed in a competing reaction.

Thus it seems

probable that in the strongly basic and nucleophilic solvent piperidine, which has the comparatively low di­ electric constant of 5.9 ,19 the concerted type mechanism proposed b y Meyer 2 7

(see p. 9) comes into play.

Table 2. A Time Study of the Reaction of Cholesteryl £-Toluenesulfonate (II) with Piperidine Total Time of Reflux, Yields of Products, m.p. Given % Accft Hours A , 163-5° B,95-8° C,oil D,72-5° for 4 24 100

6 6

7

15 20 16

(40) 38 41

15 (15) 19

(75) (80) 83

Yields are in percent; estimated yields are In par­ entheses. As It appears that second-order kinetics actually come into play,

a tentative structure for the unknown

26 cholesterylpiperidine

(B ) may be assigned.

For in ad­

dition to the usual displacement w i t h retention on chol­ esteryl £-toluenesulfonate

(II), there is the possibility

of displacement with inversion at terylpiperidine

(XXXV,

see p. 25).

to form epicholesThere is also the

possibility of an electron shift to give, for example, one of the epimeric 4-cholestenylpiperidines (XXXVI); the hydrogenation of this compound In acid solution would give,

according to the Auwers—Skita rule^ a coprostanyl—

piperidine;

this would account for the anomalous hydrogen­

ation product. Another possibility is suggested by analogy to the work of Kaiser and S w a r z ^ . esteryl £-toluenesulfonate

These workers treated chol­ (II) with sodiomalonic ester

to obtain the corresponding iycholesterylmalonic ester, which was converted by conventional means into i-cholesterylacetic acid (XXXVIII).

Compound XXXVIII, on treat­

ment with acid, readily gave a mixture of cholesterylacetic acid (XXXIX), and two Interconvertible isomers, 4 -cholestenyl- 6 -acetic acid (XL) and cholestane- 6 -acetic acid )f-lactone (XLI).

In this case the cyclopropane ring was

opened before displacement from the 6 -position could oc­ cur.

In a similar way the cyclopropane ring in compound

B could open to give 6-piperidino-4-cholestene

(XXXVII).

The series of reactions of Kaiser and Swarz are shown on p. 26

.

.CO

u* C

O

CooH XXVIII

XL

X X XIX

XL I

Of the three proposed structures for the unknown cholesterylpiperidine Bs

XXXV, XXXVI, and XXXVII (se©

below), the one preferred by the author is XXXV*

or XXXV

XXXVI

It is difficult to conceive a mechanism by which the double bond could shift from the 5- to the 4-position to give such a. c

-ound as XXXVI,

and it Is to b© pointed

out that compounds of the type XXXVII would be formed, in acid solution from i-cho1estery1 p1peridine (XXXIII);

the

time study shows that the ratio of products does not change

vlth time,

and the acid-catalyzed rearrangement of

the igcholesterylplperidine (XXXIII) in aniline solution gives the normal-type Igstaroid rearrangement* To solve the problem known compound B, the best

of the

structure of the u n ­

method of attack seems to be

the preparation of the ”nor)ialtt and Mepl” coprostany 1 piperidines#

It Is possible that one of these compounds

may prove Identical to the hydrogenation product of com­ pound B*

If so, It would only be necessary to establish

27 the position of the double bond in compound B. The reaction of cholesteryl je-tolueneiaulf onate (II) and morpholine was also studied*

Workup procedure Iden­

tical to that used for the reaction of II with piperidine was attempted,. ' However, cholesterylpiperidine

only compounds analogous to

(XXIV or A) and iycholesteryl­

piperidine

(XXXIII or B),

and cholestadiene (XXXV), were

obtained.

The failure to obtain a cholesterylmorpholine

analogous to compound B from this reaction is difficult to explain.

28 II.

The Preparation and Reactions of Epicholesterol and Epicholesteryl jD-Toluenesulfonate

Nov/ that an understanding of the stereochemistry of cholesteryl derivatives has been reached,

a study of the

reactions and the stereochemistry of epicholesterol and its derivatives can be undertaken.

(VII)

This compound Is

of considerable interest because it, like cholesterol (I) is a

-unsaturated alcohol which at first glance ap­

pears capable of an i_-steroid type rearrangement. A study of molecular models of cholesterol epicholesterol ever.

(I) and

(VII) shows one important difference, h o w ­

The A-ring in each of these compounds Is of the

trans- or chair form,

so that the methylene group

is {3 .

In cholesteryl derivatives, for example the £-toluenesulfonate

(II), the pair of electrons from C_ is in a o

position to displace the group from

by a direct back­

side attack, while in epicholesteryl £-toluenesulfonate (XLVIII) the electron pair is not in such a favorable position;

must be pushed into the O p p o s i t i o n before

the electron pair can participate in the displacement. This would give a coprostanyl-type derivative.

* +

II

XVIab

XLVIII

9

The only information in the literature on the dis-

29 placement reactions of $,£-unsatu rated £-toluene sulfonate esters is to be found in the work of S t o l l ^ , the

jd- toluene sulfonates

hexenyleyclohexanol,

who prepared

of tetrahydro-^-naphthol, £-cyclo-

and isopulegol,

and found the rates

of methanolysis of these three esters were m u c h slower than the rate of methanolysis of cholesteryl p-toluenesulfonate

(II).

This fact argues for a steric require-

ment for the neighboring group effect

43

•

Unfortunately,

however, Stoll made no effort to obtain evidence for an i^-steroid type rearrangement for any of these three $,Sunsaturated £-toluenesulfonates. Various syntheses for epicholesterol found in the literature*

(VII) are to be

It can be prepared by the oxi­

dation of the cholesteryl G-rignard reagent*^, by the acetolysis of 7-ketocholesteryl chloride followed by the WolffKishner reduction*^, or by the hydrogenation of 5-eholesten-3-one

54

or 3-acetoxycholestadiene-3,5

45

.

However,

in each of these cases a mixture of epimers is obtained; the separation of this mixture does not lend Itself to quantitative large-scale preparations,

and any Investi­

gations of the reactions of epicholesterol

(VII) would be

made somewhat uncertain by the possible presence of small amounts of cholesterol

(I).

Fortunately, however,

a synthesis was available which

appeared to give compound VII by a series of clean, specific r e a c t i o n s ^ J^ .

stereo-

This procedure was slightly mod-

30 ified to adapt it to the production of considerable amounts of epicholesterol

(VII).

The sequence of reac­

tions used for this preparation is shown on p. 31. Cholesterol

(I) was treated with peroxyphthalic acid

to obtain o(-cholesterol oxide (XLII ), which can be con­ verted by hydrogenation to 3^, 50f-dihydroxycholestane (XLIV)^;

however,

it was found more convenient to make

the isothiuronium salt with Raney nickel

(XLIII) and to remove the sulfur

The diol XLIV was treated with acetyl

chloride and dimethylaniline to prepare the diacetate XLV w h i c h could be cleanly half-saponified with methanolic sodium hydroxide at room temperature to 3$ -hydroxy-5-

o(- acetoxycholestane (XLVI). When compound XLVI was treated with £-toluenesulfonyl chloride in pyridine,

the expected u-toluenesul­

fonate was formed; however, upon heating rearrangement oc­ curred,

probably through an intermediate such as the car-

bonium ion XLVII; the product was epicholesteryl acetate, which was saponified to give the free sterol

(VII) in

overall 37% yield from cholesterol. Epicholesteryl £-toluenesulfonate (XLVIII) was pre­ pared from epicholesterol (VII) with jc-toluenesulfonyl chloride in pyridine, but proved to be rather soluble in w It was found that the preparation of the salt XLIII could be accomplished directly from cholesterol (I) in overall 55% yield without purification of the Intermediate cholesterol (X~oxide (XLII).

31

The Synthesis of Epicholesterol (VII)

oTs (I)

XLIII

XLII

------- * Const. 10 £(n _ l)j^ - n] R -i R
gg x 1Q- 4

44

£ ( * )

0. o «

.

O.oA ■

-t

Soo

/ ooo

l9oo

2 Sod Figure 3* Kinetics of the Ethanolysis of 0.0040 M (XLVIII) in Ethanol at 34. 8 ° C. 2000

1 ab 1 e 8 .

Kinetics of the Ethanolysis of 0.0040 (XLVIII) in Ethanol at 34. 8 °C.

Time, min.

15 70 145 205 345 475 625 310 1410 1755 2130

Resistance, ohms 2570000 774000 395000 281500 176900 131900 102400 81500 50943 42600 36630 K e = 8200

H o °10 r _ r

0.001 0.004 0.009 0.013 0.021 0.028 0.036 0.046 0.076 0.093 0.110

Graphical slope from Figure 3 = 0 . 4 5 5 x 1 0 ~ 4 k! = 2.303 x 0.455 x 1 0 ~ 4 = 1.05 x 1 0 “ 4 min.-l

e

45

o

4Q0 t

Figure 4. .Ethanolysis of 0.0041 M (XLVIII) in the Fresence of 0.009 M NaClO^

Table 9. Time, min. 25 62 155 250 370 610 1435

Ethanolysis of 0.0041 M (XLVIII) in the Presence of 0.009 M NaC10 4 Resistance, ohms 5010 4996 4966 4925 4878 4797 4550 Re a 3300

lo% 0

R-

0.467 0.470 0.475 0.482 0.4-91 0.506 0.561

Graphical slope from Figure 4 = 0.661 x 1 0 ' k;L a 2.505 x 0.661 x 10 “ 4 = 1.52 x 1G “ 4 m i n . “^-

46

Soo

0

Figure 5. Kinetics of the Reaction of 0.00442 Epicholesteryl jo-Toluenesulfonate (XLVIII) in Ethanol Containing 0.01179 M NaOEt at 34.8°C.

Table 10. Kinetics of the Reaction of 0.00442 M XLVIII in Ethanol Containing 0.01179 M NaOEt at 34.8°C Time, mln. 0 20

45 70 122

175 255 495 1130 1425 1915 2820

Resistance, ohms 8560 (est.) 8582 8616 3627 8635 8658 8692 8764 8910 8968 904-7 9172 Re = 9640

log

Rar

-0.426 -0.429 -0.432 -0.434 -0.440 -0.452 -0.479 -0.536 -0.565 -0.608 -0.691

Graphical slope from figure 5 = -0.968 X 10 “ 4 - "0*968 x 1 0 ~ 4 x 2.505 ko = 0.00442 - 0.01179 = 0*0302 liters/mole-min.

R

10 R e 4 0.79R

47

Ijoo

-0 .3 5 -

O

Figure 6 . Kinetics of the Reaction of 0.00425 M XLVIII in Ethanol Containing 0.00785 M Ethoxide at 34.8° Table 11. Kinetics of the Reaction of 0.00425 M XLVIII In Ethanol Containing 0.00785 M Ethoxide at 3 4 .8 ° Time, min. 0

9 69 320 420 685 915 1525 2305 3040 36000

^ enin-mQance* 9530 9536 9561 9660 9698 9791 9864 1004410229 10392 10495 R e = 11300

l o ^ m SaT?— R +0.847R (est.) -0.262 -0.265 -0.279 -0.285 -0.299 -0.312 -0.346 -0.390 -0.439 -0.475

loa

^

10 H R

0.733 0.740 0.770 0.782 0.812 0.837 0.903 0.980 1.058 1.115

G-raphlcal Slope from Figure 6 for Second Order = -0.550

k2 = S0?004g5°:50?0078§-

= °-°353 l i t e r s / m o l e - m i S ^

Graphical Slope from Figure 6 for First Order = kx s 2.303 x 1.13 x 1 0 - 4 s 2.60 x 10- 4 m in .-l

'P 10

0.4*3 4 oo

Figure 7. Kinetics of the Reaction of 0.00457 M XLVIII in Ethanol Containing 0.00461 M Ethoxide at 34.8° Table 12. Kinetics of the Reaction of 0.00457 M XLVIII in Ethanol Containing 0.00461 M Ethoxide at 3 4 .8 ° Time, Min. 0

8 20

50 115 250 355 470 605 685 1220

1385

Resistance, ohms 16960(e s t . ) 16965 16995 17040 17112 17304 17423 17526 17646 17705 18086 18205 = 23300 Re

R(Re. " f"o) Ro(Re - R) 1.002

1.C18 1.029 1.049 1.091 1.126 1.156 1*193 1.213 1.350 1.400

log. R ^10 R © ■ 0.502 0.506 0.512 0.518 0.540 0.553 0.564 0.579 0.586 0.633 0.648

Second Order slope from Figure 7 = 0.268 x 10 “ 4 v _ _ 0.268 x 1 0 - 4 . n ncQ„ , ^2 " “ '0.00457--" 0.0584 liters/mole-mm. First Order slope from Figure 7 = 0.925 x 10“4 ■^•1 “ 2.303 x 0.925 x 1 0 ”4 = 2.12 x 10"4 min.—T

49 DISCUSSIOB OP KINETIC RESULTS The reactions of epicholesteryl £-toluenesulfonate (XLVIII) thus have been shown to pursue a radically dlfferent path than those of cholesteryl jo-toluenesulfonate In the first place,

(II).

the predominant reaction of compound

XLVIII is an elimination reaction,

accompanied by a small

amount of replacement with inversion.

In the second place,

this reaction proceeds more slowly by a factor of nearly ten than does the displacement reaction on the cholesteryl derivative

(II).

The Arrhenius activation energy of these

two reactions, however,

is approximately the same, showing

that the double bond has some influence on the course of the reaction,

as Winstein and coworkers 46 have found for

the acetolysis of cyclohexyl £-toluenesulfonate an acti­ vation energy of 27 kcal.,

compared to the value of 24.8

kcal. for the methanolysis of epicholesteryl £-toluenesulfonate which was obtained in this work. Winstein and Adams

43

have also shown that the acet­

olysis of cholesteryl £-toluenesulfonate

(II) in acetate-

buffered glacial acetic acid is nicely first order.

While

our experiments with ethoxide Ion in ethanol are not exactly analogous,

It is interesting to note that second

order kinetics become of considerable importance in even very dilute solutions of ethoxide ion.

This is shown by

the fact that 0 . 0 1 2 M ethoxide ion accelerates the reac­ tion about three and a half times

(compared to pure ethanol

50 as solvent)'*, while 0.009 M perchlorate ion effects only a fifty percent increase in rate In other words,

(see Table 4, p. 36).

ethoxide ion is participating in the

reaction to a greater extent than can be explained by a "salt effect".

It would prove interesting to obtain data

on the ethanolysis and ethoxide attack on cholesteryl £toluenesulfonate

(II) Itself,

to see whether ethoxide ion

will accelerate the reaction more than the amount cal­ culated for a "salt effect". Stoll 39 has found that epicholestanyl £-toluenesulfonate

(XXVII) reacts much faster with methanol than does

cholestanyl £-toluenesulfonate

(XXVI).

Since the reverse

order of reactivity is exhibited by cholesteryl epicholesteryl

(XLVIII) £-toluenesulfonates

(II) and

(See Table 3 ),

it would be of considerable interest to determine the actual rates of these reactions under comparable con­ ditions,

as well as their activation energy and entrooy

in an effort to determine the nature and the extent of the stereochemical effects in this interesting system.

.'i.

“This value was obtained from the second order con­ stant in Table 4 byimlLta|>lying by 0.012; this giv es a pseudo first order constant, which may be compared to the firstorder ethanolysis constants.

51 EXPERIMENTAL Cholesteryl p-Toluenesulfonate (II).--

Cholesteryl

jo-toluenesulfonate was prepared by the method of Freudenberg and Hess^^.

From 50 g. of cholesterol

tained 60 g. of II, m.p. 125-132°. [lization from acetone,

(I) was o b ­

After one recrystal-

50 g., m.p. 131-3°> was obtained.

Cholesterylpyridinium £-Toluenesulfonate

(XXII).--

Compound XXII was prepared by the method of King

op

.

From

10 g. of cholesteryl jc-toluene sulfonate (II) was ob­ tained 7.6 g.

(6 6 $), m.p. 228-230°.

After one recrystal­

lization from chloroform-carbon tetrachloride,

6 g., m.p.

230-3°, was obtained. Choiesterylpiperidine o 1.27 g.

(0.002 moles) of cholesterylpyridinium £-tol-

enesulfonate 0 0 mg.

(XXIV) by Hydrogenation.—

(XXII) In 100 cc. absolute ethanol was added

of platinum oxide and a small drop of mercury.

'his suspension was shaken w i t h hydrogen at atmospheric ressure for 2 0 minutes. c.

(0.007 moles).

The takeup of hydrogen was 180

The suspension was then filtered,

and

cc. of a 2 0 $ solution of sodium hydroxide in water was dded.

The solution was evaporated to a volume of about

0 cc.,

and taken up in ether.

ashed twice w i t h water, vaporated.

The ether solution was

dried with sodium sulfate,

and

The residual white solid was crystallized

^“Melting points reported were observed on a Fisher'ohns block. Rotations were taken in a 1 dcm. tube. Anilyses were performed by Misses M. Hines, J. Sorensen, and Hobb s .

52 from acetone;

600 mg,

162°, were obtained.

(56$) of white needles* m.p.

157-

Two more recrystallizations from

acetone gave a product melting at 166-7°. Rotation:

0.0950 g. in 3 cc. of CHCI 3 gave o(~ -0.66°

( O 0 q 5 = -2 0 .8 °. Analysis: for

calculated G = 84.69, H * 12.22

found C = 84.55, H = 12.41. The mother liquors from the first recrystallization were repeatedly recrystallized from acetone, to obtain 1 0 mg.,of white platelets, m.p.

then ethanol,

141-3°.

Gholestanylpiperidine &XXV) by Hydrogenation.— One hundred mg. of cholesterylpyridinium £ - toluenesulfon­ ate (XXII) was dissolved in 30 cc. absolute ethanol, and a small amount of platinum oxide was added.

The suspen­

sion was shaken for 45 minutes with hydrogen at atmos­ pheric pressure, then filtered and worked up In the same manner as was cholesterylpiperidine lization from acetone,

50 mg.

m.p. 140-4®, was obtained.

(XXIV).

Upon crystal­

(70$) of white platelets,

A recrystallization from

acetone gave a product melting at 145-6°. 28 G h o l e s t a n o l Seven g. of cholesteryl acetate was dissolved in ether, filtered,

shaken with 1 0 g. activated alumina,

and the resulting solution was evaporated to

dryness and recrystallized from chloroform-methanol.

This

procedure was adopted after numerous hydrogenations had failed due to poisoning of the catalyst.

The purified

53 cholesteryl acetate was dissolved in a mixture of 40 cc. of absolute ether and 60 cc. of purified glacial acetic acid. Two hundred mg. of platinum oxide were added, and the sus­ pension was shaken under a pressure of 50 potinds of h y ­ drogen in a modified Parr apparatus for two hours.

The

hydrogen was then replaced by air and the suspension was filtered.

The solvent was evaporated and a solution of 10

g. of sodium hydroxide in 2 0 0 cc. of ethanol was added. Saponification of the ester was complete after one h o u r ’s reflux;

at this point water was added until the solution

became quite cloudy; when cooled and filtered, 5 g. of amorphous white solid, m.p. 120-130°, was obtained. Two g. of this hydrogenation product was dissolved in 20 cc. of a 0.5 M solution of peroxyphthalic acid in e the r (see p . 6 7 ), and allowed to stand in the dark for three hours at 25°. air stream,

The ether was then evaporated in an

and a solution of sodium hydroxide and sodium

thiosulfate in water was added. extracted w i t h ether, w ith water, dryness.

The suspension was then

and the ether layer was washed, twice

dried w i t h sodium sulfate,

and evaporated to

Upon crystallization from acetone-water was ob­

tained 1 . 6 g.

(80/S based on impure starting material),

m.p. 140-2°.

This was dissolved in ether and chromato­

graphed on a six-inch column of activated alumina with 30 cc. holdup.

The first four elutions with 30 cc. of

ether each gave no solid material; the fifth and. sixth,

54 w h e n combined,

gave 1.5 g. m.p. 141-3°.

Cholestanyl jj-Toluenesulfonate.— g. of cholestanol, m.p, 141-3°,

One and one half

and one g. of £-toluene-

sulfonyl chloride were dissolved in 10 cc. of dry pyridine and allowed to stand overnight. was added one cc. of water; served,

To the resulting solution

an exothermic reaction was ob­

and after about five minutes excess water was added;

the suspension was filtered,

and the gummy solid was taken

up in ether and w ashed with water.

The ether solution was

dried with sodium sulfate and evaporated to dryness.

The

residue was crystallized from ethanol to obtain 1.9 g. (90$) of white platelets, m.p. 135-6°.

Reported^® m.p.

136°. Epicholestanylpyridinium pyfoluenesulfonate (XXVIII).— A solution of 1.9 g. of cholestanyl js-toluene sulfonate (XXVI) in 10 cc. of pyridine Steam bath.

was heated overnight on the

The pyridine was evaporated in an air stream

and the resulting solid mass was recrystallized from ace­ tone, to obtain 2 g., m.p. 160-170°.

This was dissolved in

chloroform and the solution was washed with a solution of 10$ ethanol In water.

The chloroform solution was dried

w ith sodium sulfate and the chloroform was removed on the steam bath.

The residue was

g.

white platelets, m.p. 165-170°, were obtained;

(45$) of

crystallized from acetone; one

this product was used directly In the following hydrogenation without purification.

55 2-Qholestene.—

The acetone-soluble fraction from

the preparation of the pyridinium salt (XXVIII) was evap­ orated to dryness, leached w ith Skellysolve B, and f i l ­ tered.

The filtrate was evaporated to dryness,

and the

residual oil was crystallized from acetone-water, then from acetone;

in this manner 2 1 0 mg.

(16%) of needles,

m.p, 67-8°, were obtained. Rotation: = +60.3?

103.0 mg. in 3

cc.of CHCl^ gave 0 6 * ♦ 2.07.

( O 0 5 7 8 0 ■= *64°,

< © < ) 5 4 6 0 = *71°,

(Ctf4358 =

= -*122 °. R e p o r t e d ^ m.p. 68-9°,

(C^Op) - +64°, for 2-chole stene.

Epicholestanylplperidine

(XXX) by Hydrogenation.—

Pour hundred mg. of epicholestanylpyridinium £-toluenesulfonate

(XXVIII) and 100 mg. of platinum oxide in 30 cc.

of absolute ethanol were shaken with hydrogen at atmos­ pheric pressure

for one hour. The

culated 52 ml.

The suspension

takeup was 66 ml.; cal­

was filtered,

and the fil­

trate was worked up in the same manner as for cholesterylpiperidine (XXIV,

see p. 51).

On crystallization from

acetone-water, 210 mg., m.p. 85-90° (85%), was obtained, after two recrystallizations from acetone-methanol a prodct was obtained which melted at 96-8°. Rotation: 81.4 mg. (O0p4 =

in 3 cc. of CHCl^ gave 0(= +0.69°.

Analysis: for 0 5 g H 57 N, calculated

2 = 84.31, H a 12.61, N = 3.07; found C = 85.1, H = 13.1, 1 * 3.65.

The consistently high analyses seem to be typi-

56 cal of this type of compound, be observed on p.

as the same difficulty will

for the normal cholestanylpiperidine

(XXXI). Epicholestanylpiperidine

(XXX) by Displacement.—

One hundred eighty mg. of cholestanyl £-toluenesulfonate (XXV'l) and 5 cc. of piperidine were heated on the steam bath for two days; then two pellets of sodium hydroxide were added and the solution was steam distilled to remove the excess piperidine. washed w ith water, evaporated. tone,

The residue was taken up in ether,

and the ether solution was dried and

The residue was taken up in 20 cc. of ace­

and the solution was saturated with dry HC1 gas

and evaporated to dryness.

The solid residue was leached

with Skellysolve B and filtered;

the residue was decom­

posed w i t h alcoholic sodium hydroxide, taken up in ether, and the ether solution was washed with water, evaporated.

dried, and

After one crystallization from acetone-water

was obtained 80 mg.

(53$) m.p. 98-100°.

A recrystalliza­

tion from acetone-methanol gave a product melting at 99-100°. Rotation: =

53.8 mg. in 3 cc. of CHC1 3 gave 0(= t0.47°; Mixed m.p. with the hydrogenation pro­

duct from p. 55 was 96-8°. The Skellysolve B.-soluble fraction was crystallized from acetone-water to give a product melting at 64-5°. Mixed m.p, with a sample of 2 -cholestene from p. 55 was 67-8°.

57 Epicholestanol.--

Five hundred mg.

js-toluene sulfonate (XXVI), m.p* 135-6°,

of cho lestany 1 and 500 mg. of

fused potassium acetate were dissolved in 30 c c . of glacial acetic acid and the solution was refluxed for eight hours. The acetic acid was removed in an air stream and the re­ sulting oil was taken up in ether. was washed twice w ith water, and evaporated to dryness.

The ether solution

dried with sodium sulfate, A solution of one g. of so­

dium hydroxide in 50 cc. of methanol was then added, and the resulting solution was refluxed for two hours. methanol was then evaporated nearly to dryness, residue was taken up in ether-water. separated, water,

The

and the

The layers were

and the ether layer was washed twice with

dried,

and evaporated.

The residual solid was

then taken up in 50 cc. of Skellysolve B and. chromato­ graphed on an activated alumina column 8 inches in length with a holdup of 25 cc. Fraction 1 2 3 4

Eluant

Obtained

50 cc. Sk-B 100 mg. 50 cc. Sk-B 80 mg. 50 cc. Sk-B 2 mg. 25 cc EtgO-25 c c .CHC15 140 mg.

M.P.

67-8°, 68° oil 181-4° (40%)

Fractions 1 and 2 were combined and crystallized from acetone-water to give a product, m.p. 64-6°; mixed m.p. with 2 -cholestene from p. 55 was 65°. Fraction 4 was crystallized from methanol-chloroform to give 80 mg., m.p. 183-4°. Rotation: 75.6 mg. in 3 cc. of CHCI 3 gave c