July, 1964
PREGSAXE ~~-THIOESTERS
331
Synthesis of Some Pregnane 16-Thioesters LELAXDI,. SMITHA N D DANIEL 11. TELLER Research and Dezielopnient Ditsision, T y e t h Laboratories, Inc., Radnor, Pennsylzlania XeceiLed December 11 1963 I
I,4-hddition of thioacids to 16-dehydropregnane 20-ketones affords 16-acylthio 20-ketones with steric. result,s dependent on the steroid and the thioacid involved. Both 1601- and 160-thioesters result. The structures of the thioester products have been assigned on the basis of proton nuclear magnetic resonance and optical rotatory dispersion spectra.
I:or studies relating mineralocorticoid activity to 16-dehydro 20-ketone syst'em depends on both the substitution a t the C-16 position iii the pregiiaiie st'ructure of the steroid aiid the thioacid. Since the nucleus, we desired to have certain analogs of I(iaaddition of thioacids t'o the A l - and A6-double bonds of oxygenated steroids. Of particular iiiterest were the and A4,6-3-ketones y s t e m is known to give both 16a-thio analogs of 16a-hydroxycortexone (16a,21possible epimeric 1- arid 7-thioester products; and addidihydroxypregn-4-eiie-3,20-dione) and the sodiuni extion of thioacetic acid to 3fl-acetoxypregna-5,16-dieiicreting factor (3~,16a-dihydroxy-5a-pregiia1i-20-oiie)20-one affords three of the four possible jsoiiieric 16-thioesters,*' it was anticipated that 16,17-isonieric of Seher, et al.' 1:or their synthesis the well-knon-n 1,4-addition of products would be eiicountered in t'he present study. Indeed, two crystalline thioesters T'IIa aiid TTIIa, substituted thiols to 16-dehydropregiiaiie 20-ketones readily differentiated from oiie another by their was chosen.* Specifically, addition of thioacids and of iiieltiiig point behavior aiid infrared and iiuclear hydrogen sulfide to select 16-dehydropregiiane 20magnetic resonance spectra but not separable 011 thin ketones resulted in the forniation of 16-thioester and 16-niercapto derivatives of the type sought. layer chroniatograms, were isolated froiii the reactioii The reaction between steroid aiid neat thioacid of thioacetic acid and 3P-hydroxy-$3-pregii-16-en-20began iinniediately after solutioii was effected, mild one (IVa). Two of the three kiiowii isoiiieric 10heat evolution occurred, and the reaction was complete thioesters derived from SP-acetoxypregna-5,16-dien-20within minutes. Only very small aiiiouiits of starting one and thioacet'ic acidYfwere obtained (XI and XIIj. Thioester X I isomerizes t'o the iilore st,able l6ainaterial could be detected by thin layer chroniatogacetylthio-17P-pregiiaii-20-one XII, ?' and we have raphy or by ultraviolet light absorption spectra in the isomerized with concomitant acetylation the thioester reaction niixture after this tiiiie. 'Ihe reaction also J'IIIa with sodiuin acetate and acetic acid t o the 1Gaoccurred in niethyleiie chloride solutioiis of steroid and thioester T'IIb. t hioac id. The resultant thioester derivatives 11, 111, T.11, I n other cases we were uiiable to obtain more than oiie crystalline thioester from the reaction inixtures, T'III, IXa, X I , XII, aiid XI11 thus prepared were although low yields, difficultly purified products. and assigned the 16-acylthio 20-ketone structure on the basis of elemental analysis and ultraviolet aiid infrared nuclear niagnetic resonance spectra indicated that absorption spectra. The thioesters T'II, VIII, IXa, isomeric thioesters had been forined. The apparent isoiiier coiiiposition of the thioester reaction products X I , XII, and XI11 exhibit selective ultraviolet absorpis presented iii Table I. tion typical of such derivatives3 and infrared carboiiyl and C-S stretching bands characteristic of thioaceThe several thioesters prepared in t'liis study can be tates.? 1 ' he thiopropionates IIIa, IIIc, and T'IIIb grouped into two sets depending 011 their protoii nuclear inagiietic resonance spectra. The first group absorb iiear 10.7 ,u.~>' consists of thioesters 11, T'II, IXa, XII, and XIII, The stereoselectivity with which thioacids add to the aiid is characterized by the proton resoriances: C-18 (I) (a) R . Neher, P. Desaulles, E. Vischer, P. TVieland, and A. Wettstein, methyl at 0.60-0.76 p.p.m.,6 C-21 niethyl a t 2.12-2.17 He1.i. Chim. Acta, 41, 1667 (1958); (b) R . Neher, C . Meystre, and A. Wettp.p.m., 16-thioacetate iiiet,hyl a t 2.23-2.28 p.p.iii., stein, ihid.. 42, 132 (1939). 17-proton doublet at, 2.39-2.67 p.p.iii., and 16-prot'on (2) (a) R. Bourdon and C,. Rosseels, P m d . Pharm.. 16, 425, 471 ( I g ( i 1 ) ; ( b j .J. Romo. 11. Romero. C . Iljerassi. and G . Rosenkranz a t 4.2.5-4.28 p.p.in. Except for the l(i-proton and Clirm. S o c . , 73, 1.i28 (1931); i c ) .J. Romo, (;. Roeenkranz. and C. Iljerassi, thioacetat,e iiiethyl resoiiaiices, these spectra are typical ibid., 73,4Rlil (lY,?l); ( d ) .J. Romo and G . Contreras. Bol. Inst. Quim. 7 . n i i . . S a l . Au/o,i. . l I e ~ . ,4 , 101 (19.72); ( e ) C:. Rosenkranz. C . Ujerassi. and .J, of those obtained with 16a-hydroxy and acetoxyRomo, V. S. Patent 2.(397.308 (I)ec. 1 4 , 19,74j; ( f ) R. 11. I h d s o n and P. 13. substitut,cd 17~-pregiiaiie-20-ketoiie~.~ dollman, U. S. I'atent 2,Q12,443 (Xov. 10. 19.59); ( a ) H. Reimann and IC. I.. Sliapiro, U. S . I'atent 2,928..5.57 (June 1.3. IHlil); (hj -1. d. Hoffman, H. 31. Kissman, and M. J. IVeiss, .I. Med. Pliarm. Chem., 6 , 9(j2 (1962). (3) Steroid tliioacetates absorb in the region. 230-237 mp ( e 3500-IiOOO) : see (a) S. Bernstein and K. J. Sax, J . Org. C h i m . , 16, F85 (1951): (b) C. Djerassi and A. L. Nussbaum, J . A m . Chem. Soc., 75, 3700 (1953); ( e ) T. Komeno, Chem. Pharm. Bull. (Tokyo), 8, 608, 672. 680 (1960); (d) T. Komeno, U. S. Patent 5,016,386 (Jan. 9 , 1962): (e) I(. Takeda and T. Iiomeno, Chem. Ind. (London), 1793 (1902). (4) Steroidal thioacetates absorb in t h e region 5.87-6.04 and 8.77-9.1 p ; see (a) R . 11. Doilson and R . C. T u e i t , J . .4m. Chem. S o e . , 81, 1224 ( 1 9 5 9 : ( h ) R . Hourtion and 3 . Ranisteano, Bull. soc. chim. F r a n r r , 1982 ( l 9 f i O ) ; ( c ) R . E. Srharib and AI. .J. JVeiss, .I. O w . Cliem., 26, 1223. 3915 (lUlilj; (d) ref. IOa-IOd; (e) 1'. C. Uhle, J . O r g . Chem., 27, 2797 (19W).
(a) It. C:. Tweit. i t i d , , 27, 2ti93 (1902); (b) R . C . T n e i t , I?. E. Culton, (i) X. L. AIcXiren. and W.Iilyne, ihid.. 27, 332.; (1962). ( i j ) Proton niiclear magnetic resonance spectra were obtained on 10-1 Z R solutions of steroids in deuteriochloroform with tetramethylsilane as a n internal reference, using a Varian Associates Model A-60 spectrometer (GO Me.). T h e resonance lines are measured from the internal reference in a downfield direction. (7) Several 16a-hydroxy-17b-pregnane20-ketones have C-18 methyl resonances a t 0.62-0.65 p.p.m,, C-21 methyl a t 2.13-2.18 p.p.m., l i e - p r o t o n a t 2..51-2.0R p.p.m. (doublet, J = 6-7 c.p.s.), IRp-proton a t 4.7.?ri.00 1J.p.m. (multiplet), Unsubstituted 17P-pregnane 20-ketones have C-18 methyl resonances a t 0.80-0.71 p.p.m., C-21 methyl a t 2.11-2.15 p.p.m., 170proton a t 2.4li-2.47 p.p.m. (doublet, J = 8-Y c.P.s.).
\
COCH3
aF-
"SCOCH,
13'0
NaOAc-HOAr
COCHi
"SR
@ \ SCOR
HO
H
HO
H
H
VIIa, R' = H
VIIIa, R = ( ' H i
IXa, R = COCH3
VIIb, R1= COCH:
VIIIh, R
IXb, R - H
@OCH
Hi
~
-0COCH
Ho
\
X
& J O ( H 3
HOCH20COCH3
SCOCH 1
C H \COO
H
- G2H5
'-SCOCH j
('H3COO'' XI
SCOCHj
CH3COO
XI1
XI11
I’REGKANE ~ ~ - T H I O E S T E R S
.July, 1964
X33
TABLE I STEREOSELECTIVITY OF ADDITIOX OF THIOACIDS 16-Dehydro 20-ketone
Thioacid
Methoda
Isomer isolatedh
Yield,
Iso 111c 1
52 34 52 62
ratioe
A 9: 1 Thioacetic 160 ( I I I b ) 16p (IIIc) Thiopropionic A 4 :1 A 16a ( I I b ) 0: 1 Thiobutyric loa ( I I a ) i2 Pl-Aretoxypregna-4,16-diene-3,20-dione (Ia) Thioacetir B I :7 39 16p (IIIa) B ... Thiopropionic 37-49 1:l B 16a (1TIa)“ 3P-Hydroxy-Sp-pregn-16-en-20-one (11-a) Thioacetic 60 A 16cu (T-IIa) ... Thioaretic 52 16p (TTIIb) B 7 :1 Thiopropionic 60 16a ( I S a ) B 1:s 3p-Hydroxy-5a-pregn-16-en-20-one Thioacetic 16p ( X I ) ” 60 A 13: 1 3p-Aretoxypregnad, 16-dien-20-one Thioacetic a .4,neat thioacid warmed 5-30 min. on a steam bath; B, methylene chloride solution plus thioacid, 0.5-3 hr. a t room temperahre. a Only one isomer was readily isolated pure from a givcn reaction mixture. c I n certain experirnenh the 16p-isomer was isolated in 53-64(,’; yields, isomer ratio ca. 1 : 1. d In one experiment a low yield of the 16a-isomer was obtained. e The isomer ratio, defined as the ratio of the 1Bp-isomer content to the 16a-isomer content, was determined by nuclear magnetic resonance analysis of total reaction producte, mother liquor fractions, etc., on the assumption that spurious lines in the C-18 methyl region (0.60-0.96 p.p.m.) not present in spectra of the pure isolated isomer were due to the presence of 16-isomeric produrts. Pregna-4,16-diene-3,20-dione (Ib)
acetylthio-3P-hydroxy-5Pl17P-pregnan-80-one, and X I other 16a- and 16,B-acetoxy-17,B-pregiiane 20-ketone must be 3P-acetoxy-l6~-acetylthio-17P-pregn-T,-en-20-pairs. l1 Analysis of the proton nuclear magnetic resonance one. spectra of these thioesters also supports the 16pBy analogy other members of the group are assigned the 1G~-acylthio-17~-pregnan-20-onestructure. Alacylthio-17P-pregnan-2O-one structure. Whereas the though the A X u values for the 16-thioester functional downfield shifts of the C-18 methyl group protons to group in these cases are negative and of the same 0.87-0.96 p.p.ni. (relative to 0.60-0.71 p.p.m. for order (-195 to -309) found for the 16a-thioester simple 17P-pregnane 20-ketones and 0.60-0.76 p . p m . group, the molecular rotational differences for the several 16a-thioesters) is characteristic of 17afor the isonieric pairs VIIa-VIIIa and XII-XI are pregnane 2 0 - k e t o i i e ~ other ,~~~~ aspects ~ of the spectra +SI and +go, respectively, which is in accord with are not in accord with a 17a-pregnane formulation. Thus the C-21 methyl protons in 111, YIII, and XI are found upfield froni their position in siniple 17apregnan-20-one derivatives,Sh l 2 in 17P-pregiian-20one derivatives, and in the 16wthioesters. This increased shielding of the C-21 methyl protons thus cannot readily be associated v i t h isoiiierization of the C-17 side chain. Furthermore the 17-proton doublet in this set of thioesters a t 2.83-2.86 p.p.ni. is unshjelded in comparison Jyith the l7a-proton of the l6a-thioesters and of 16a-hydroxy-17,B-pregnan-20-oiie derivatives (2.51-2.66 p . p . n ~ . ) . ’ ~ The downfield shift of the C-18 methyl protons in the I6P-thioesters is also characteristic of 1,3-diaxial interactions between the C-18 protons and 8P-, lib-, and 15P-hydroxyl groups aiid between C-18 protons and IlP- and 15p-acetoxyl groups.14 .+lthough the 16p-acylthio feature cannot be considered axial, its l13-pseudo-axial relation to the C-18 methyl group should lead to a deshielding iiifluence.Ij The three effects of increased shielding of the C-21 methyl protons, of decreased shielding of the 17-proton, and of decreased shielding of the C-18 methyl protons
-6
I
I
1
1
I
1
I
250 270 290 310 330 350 370 390 410 4 X (mF) Fig. l.-Optical
rotatory dispersion spectra.
(11) Akfn (lRP-acetoxyl-l6a-acetoxyl) values range from f 0 7 to +4lO.sd (12) C-18 methyl protons in simple 17a-pregnane 20-ketones h a r e been reported a t 0.85-1.02 p.p.m.; see (a) W. J. Wechter and H. C. hlurray. J . 0 7 0 . Chem., 28, 755 (1963); (b) P. CrabbP and J. Romo, Bull. aoc. c h i n . Belges, 72, 208 (1963); (c) J. E. Pike, G . Slomp. and F. A hlacKellar, J . Org. Chem., 28, 2502 (1963). (13) I t must be noted, hoaever, t h a t the 17p-proton in some 17o-pregnane 20-ketones has been found as a doublet a t 2.92-3.19 p . p . m . with J = 7.5 c.p.s.’Zd (14) (a) Y. Kawazoe, Y.Sato. M. Natsume, H. Hasegaaa, T. Okamoto. and K. Tsuda, Chem. Pharm. BuZ1. (Tokyo), 10, 338 (1962); (b) K. Tori and E. Kondo, Te!rahedron Letters, NO.10, 645 (1983). (15) The 166-acetoxyl group of two pregnane 20-ketones show a deshielding effect on the C-18 methyl protons; see compounds no. 132 and 134 in R. F. Ziircher, HelL’. Chzm. Acta. 46, 2054 (1903).
July, 1964
P R E G S A S E 16-THIOEGTERS
the solvents were removed under vacuum. The gummy residue !vas crystallized and rerrystallized from ethanol three times, yielding 1.0 g. of product, m.p. 161-162". Chroniatographyon silica gel (elution with 10% ether in benzene) afforded the analytical sample, m.p. 162-164'; [CY]D +94.8°*s;, , ,A 238 mp (E 19,400); ::A: 5.74, 5.79, 5.95, 6.03, 6.22, 8.17, 9.01, and 10.61 p, etc.; Rt 0.34 in system Ia, 0.23 in system IIIa. A n d . Calcd. for C2,&40$: C, 67.23; H, 7.67; S, 7.18. Found: C, 67.35; H, 7.39; S, 6.84. Xuctlear magnetic resonance spectra: C-18 methyl a t 0 . i 6 p.p.ni.: C-19 methyl at 1.18 p.p.m.; C-21 acetosyl methyl a t 2.17 p.p.ni.; 16a-thioacetate methyl a t 2.28 p.p.m.; lia-proton a t 2.61 p.p.m. (doublet. J = 9 c.P.s.): l(i(3-proton at 4.28 p.p.ni. (triplet of doublets); C-21 methylene at 4.63 p.p.m. (quartet, J = 1i'c.p.s.); 4-protonat5.iE1p.p.m. 16~Butyrylthiopregn-4-ene-3,20-dione (IIb).-lg-Dehydroprogesterone ( I b ) ( 2 g.) dissolved in 5 ml. of technical thiobut,yric acid was warmed on a st>eambath for 15 min., after which time the thioacid was removed under vacuum. The yellow gum obtained was crystallized from ether-methanol, 920 mg., m.p. 150-152". A second and third crop, 420 mg., m.p. 148-150", and 300 nig., m.p. 134-139", was taken. Recrystallization from ethanol and from acetone gave the pure product, m.p. 152-153.5'; ID +40.5'; A,, 239 nip ( E 20,200): :A: 5.84, .5.95, 6.01, and 6.18 p , etc. dnal. Calrd. for Cj3H3603S: C, 72.07; H, 8.71: S, 7.70. Found: C, 72.17: H,8.67; 8, 7.68. Suclear magnetic resonance spectra: (3-18 methyl a t 0.71 p.p.m.: 16e-thiobutyrate met'hyl a t 0.93 p.p.m. (triplet, J = 7 c.P.s.); C-19 methyl a t 1.20 p.p.m.; C-21 methyl at' 2.17 p.p.m.: 17a-proton a t 2.62 p.p.m. (doublet, J = 9 c.p.s.); 16sproton a t 4.26 p.p.m. (triplet of doublets); 4-proton a t 5.73 p.p.m, 16a-Acetylthio-6a-methylpregn-4-ene-3,2O-dione (IIc).-6eSlethylpregna-4,16-diene-3,20-dione(IC) (4 9.) was treated by the procedure used for IIa. The resultant oil was crystallized from 2-propanol, yielding 3.2 g. of product, m.p. 158-160'. Several recrystallizations from 2-propanol afforded the pure ~ A,, 238 nip ( E 19,700); product, 1n.p. 160-161"; [ a ]-I-31.5'; ::A: 5.87, 5.93, 6.01, 6.23, 7.37, 8.87, and 10.45 p, et(..; Rf 0.81 in system Ia, 0.42 in system IIIa. Anal. Calcd. for C?aH&S: C, 71.60; H, 8.51; S, 7.96. Found: C, 71.79; H, 8.32; 8,7.80. Nuclear magnet,ic resonance spectra: C-18 methyl a t 0.72 p.p.m.; 6a-methylatl.06 p.p.m. (doublet, J = 6.5 c.P.s.); C-19 methyl a t 1.18 p.p.ni.; C-21 methyl at 2.16 p,p.m.; 160-thioacetate methyl a t 2.27 p.p.m.; lie-proton a t 2.63 p.p.m. (doublet, J = 9 c.P.s.); 16p-proton a t 4.28 p.p.m. (t,riplet>of doublets); 4proton a t 5.80 p . p m . 21-Acetoxy-16p-propionylth~opregn-4-ene-3,2O-dione (IIIa).Gsing the procedure for IIa, except that technical thiopropionic acid was substituted for thioacetir acid, 3.0 g. of 21-acetouypregna-4,16-diene-3,20-dione(Ia) was converted to 1.5 g. of (.rude 16p-thiopropionate, m.p. 118-121". After chromatography on silica gel (elution with 570 ether in benzene) the pure thio~ A, propionate was obt,ained, m.p. 129-131"; [ a ]f61.5': 238 mp ( E 18,500);: : :A 5.72, 5.78, 5.95: 6.02, 6.20, 8.15, 9.49, and 10.65 p , etc.; Rf 0.36 in system IIa. Anal. Calcd. for C26H3606S: C, 67.79; H, 7.88; S, 6.96. Found: C, 67.81; H,7.86; S,6.88. Nuclear magnetic resonance spectra: C-18 methyl a t 0.87 p.p.m.; 160-thiopropionate methyl at 1.15 p.p.m. (triplet, J = 7.5 c.P.s.); C-19 methyl a t 1.18 p.p,m.; C-21 acetoxyl methyl a t 2.20 p.p.m.; 16p-t,hiopropionate methylene a t 2.53 p.p.ni. (quartet, J = 8 c.P.s.): 16a-proton a t 4.28 p.p.ni. (niu1t)iplet); C-21 methylene centered at 4.63 p.p,m. (quartet,, J = 17 c.p.s.); 4-proton a t 5.75 p.p.m. 16p-Acetylthiopregn-4-ene-3,20-dione(IIIb).-A solution of 4.0 g. of 16-dehydroprogesterone ( I b ) in 4.0 ml. of technical thioacetic acid was warmed on a steam bath for 20 min. The t,hioacetic acid was removed under vacuum, and the gummy residue was washed with water and crystallized from ethanol, yielding 1.66 g. of product, m.p. 172.5-176.5'. After several recrystallizations from ethanol the pure product was obtained, m.p. 184-185': ["ID +81": A,, 239 m p ( 6 20,000); ::A: 5.8.5, -5.93, 6.01, 6.20, and 8.90 p , etc.; A ~ s after ~ 2 hr. (29) Hoffman, et aZ..2h report m.p. 153-155' and [O]D + 7 1 ° for I I a . T h e LID and ALIn values calculated by these investigators are in error and should read ID f317, A A I D -37.5.
333
290 (543), 400 mF (30); Rr 0.59 in system In (Rr of Ib is 0.74), 0.84 in propylene glycol-toluene. Anal. Calcd. for C23H3203S: C, 71.09; H, 8.30: S, S.25. Found: C, 71.15; H,8.23; S,8.30. Nuclear magnetic resonance spectra: C-18 met,hyl at 0.96 p.p.m.; C-19methylat 1.20p.p.m.; C-21 methylat 2.07p.p.m.; 16p-thioacetate methyl at 2.32 p.p.m.; lie-proton a t 2.86 p.p.ni. (doublet', J = 10 c.P.s.); 160-proton a t 4.28 p.p.ni. (quartet); 4-proton a t 5.75 p.p.m. 16p-Propionylthiopregn-4-ene-3,20-dione (IIIc).-Two grams of 16-dehydroprogesterone (Ib) \vas dissolved in 30 ml. of terhriical thiopropionic acid and after 5 niin. on the steam bath the thioscid was removed under vacuum. The g u m obtained was c-rystallized from ethanol, yielding 990 mg. of material, n1.p. 239 mp it 19,000), from which an analytical l56-l5Y0, A,, +71.4"; A,, sample was prepared, n1.p. 163.5-164.5'; 239 mp ( E 21,400); ::A: 5.89, 5.93, 6.02, 6.21, 9.22, and 10.7 p, etc30 Anal. Calcd. for C24H3403S: C, 71.60; H, 8.51; S, 7.96. Found: C,71.68; H, 8.63; S, 7.50. Xuclear magnetic resonances spectra: C-18 methyl a t 0.9G p.p.m.; C-19 methyl a t 1.18 p.p.m.; 168-thiopropionate methyl at 1.16p.p.m.(t,riplet,J = 8c.p.s.); C-21methylat2.06p.p.ni.; 168-thiopropionate methylene a t 2.53 p.p.m. (quartet, J = 8 r.p.s.); 16a-proton a t 4.30 p.p.ni. (multiplet); 4-proton a t 5.75 p.p.ni. 16~-Acetylthio-3p-hydroxy-5p-pregnan-20-one (VIIa).-To a solution of 1 g. of IVa in 50 nil. of methylene chloride was added 10 ml. of technical thioacetic acid. After 3 hr. a t room temperature the solvents were removed under vacuum and the residue rrystallized from cyclohexane-petroleum ether yielding 300 mg., m.p. 127-129"; ID f8.9'; A, 233 mp ( E 4720);: : :A 5.84, (E;:m) 5.99, 6.91, 7.39, 8.92, 9.69, and 10.45 p , etc.; A,":04 after 2 hr. 286 (42), 347 (33))382 (31), and 456 mp (26); Rf 0.32 in system IIIa, 0.54 in system Ia. -4nal. Calcd. for C23H3603S: C, 70.36; H, 9.24; S, 8.17. Found: C,70.52; H,9.40; S, 7.70. Nuclear magnetic resonance spectra: C-18 methyl a t 0.66 p.p.m.; C-19 methyl a t 0.95 p.p.m.; C-21 methyl a t 2.12 p.p.m.: 16a-thioacetate niethyl at 2.26 p.p.m.; lia-proton a t 2.62 p.p.ni. (doublet, J = 8.5 c.p.5.); 16P-prot'on a t 4.26 p.p.m. (triplet of doublets): &-proton a t 4.13 p.p.m. (broad). Optical rot'atory dispersion: [alaa +20°, [a]311 +1950", and [ a ] ~ ,-5450'. o Reaction of 1.0 g. of IVa in 2.0 ml. of neat technical thioacetic acid with warming for 5 min. afforded 740 mg. (60yG)of crude 233 mp ( e 4700). thioester TIIa, m.p. 124.5-125.5'; , , ,A 3p-Acetoxy-16a-acetylthio-5p-pregnan-20-one(VIIb). A. By Thioacetic Acid Addition.-A solution of 3 g. of 3p-acetoxy5p-pregn-16-en-20-one (IVb) in 75 ml. of methylene chloride and 30 ml. of t'echnical thioacetic acid was held a t room temperature for 30 min. and the product was isolated in the usual manner. After chromatography on silica gel (elution with 2% ethyl acetate in benzene) the pure product was obtained, 540 mg., n1.p. 140-158"; ID +18.3"; , , ,A 232 m p ( E 4500); ::A: 5.78, 5.85, 5.93, 6.92, 8.00, 8.03, 8.10, and 8.83 p, etc.; Rf 0.92 in system Ia, 0.80 in system IIIa. dnal. Calcd. for C25Haa04S: C, 69.08; H, 8.81; S, 7.38. Found: C, 69.47; H, 9.02; S, 7.36. Nuclear magnetic resonance spectra: C-18 methyl a t 0.65 p.p.m.; C-19 methyl a t 0.98 p.p.ni.; 3p-acetoxyl methyl a t 2.05 p.p.m.; C-21 methyl a t 2.14 p.p.m.; 16a-thioacetate methyl a t 2.26 p.p.m.; 17a-proton a t 2.62 p.p.m. (doublet, J = 8 c.p.s.); l6p-proton at 4.25 p.p.m. (triplet); 3a-proton a t 5.11 p.p.m. (broad). Optical rotatory dispersion of T I I h : [ a ] 4 z s+47", [ a 1 3 1 0 -t 1530", and [a1260-5270'. B. By Isomerization.-l6~-Acetylthio-3p-hydroxy-5p-pregnan-20-one (VIIIa) (200 mg.) dissolved in 3 ml. of glacial acetic acid containing 200 mg. of anhydrous sodium acetate was refluxed. After 15 min. a sample was taken, diluted with water, and extracted with chloroform; the extracts were dried and evaporated. After 3 hr. a second sample was taken and treated in the same way. Nuclear magnetic resonance spectra of the first sample indicated a ratio of VIIIa to T I I a of 3: 1. The second sample was identified as pure T I I b by nuclear magnetic resonance and by thin layer chromatography. (30) Dodson and Sollman report a 16-propionylthioprogesterone,m.p. 134-135O; Bee ref. 2f.
(doublet, J = 9 c.p.s.); 16P-proton a t 3.76 p.p.ni. (multiplet); 3a-proton a t 5.10 p.p.m. Further elution of the column with 5 5 ether in benzene gave 120 nig. of the thiol l T a ,crystallized froni hexane, m.p. 168-171"; x~J:' 5.86, 6.{)1>7.40, and $1.70 p , etc.; Z i i 0.73 in system Ia, 0.70 in system I I I a . 2lnal. Calcd. for C,,HlaO C, 71.95; H, 9.66; S, 9.15. Fniintl: C, i1.8X; I%,9.(jO; e, Both thiols 1.a mid 1%gave a violet-red color with sodiuni nitroprusside solution and decolorized a carbon tetrachloride solution of iodine. Acetylation of 1-a n i t h excess acetic anhydride in pyridine in the usual manner gave the acetoxy thioester VIIb, m.p. 154157", identical in infrared and chromatographic properties with 1 T I b prepared from 11-b. 16~,16a'-Dithiobis(3~-hydroxy-5p-pregnan-2O-one) (VI).A solution of 400 mg. of t h e thiol-disulfide mixture (Va and VI) dissolved in 100 ml. of benzene and 50 nil. of water was treated with a solution of iodine in benzene until a slight excess of iodine was present. Aqueous sodiuni thiopulfate was added to destroy the excess of iodine and the organic layer was separated, washed with water, and dried over anhydrous magnesium sulfate. Evaporation of the solvent afforded a guni which v a s crystallized from benzene-hexane, yielding 140 mg. of disu!fide, m.p. : : ! A 5.90, 6.92, 7.40, 8.12, and 9.71 p j etc.; Xi 0.70 171-178"; in system Ia, 0.18 in system IIIa. Anal. Calcd. for C ~ ~ H G G OC,~ S72.16; ~: H, 9.52; S j 11.17. Found: C , i 2 . 2 7 ; H,9.28; S, 9.20. Nuclear magnetic resonance spectra: C-18 methyl a t 0.60 p.p.ni.; C-19 methyl at 0.05 p.p.m: (3-21 methyl a t 2.18 p.p.m.; lia-proton a t 2.71 p.p.m. (doublet, J = 8 c.P.s.); 160-proton at 3.88 p.p.ni. (multiplet); Sa-proton a t 4.13 p.p.m. (broad). 3p-Hydroxy-16a-mercapto-5a-pregnan-ZO-one(IXb).--A solution of l .O g. of 3p-hydrosy-5a-pregn-16-en-20-one in 25 ml. of pyridine and 0.09 nil. of piperidine was alternately flushed with nitrogen and evacuated four times. Hydrogen sulfide was bubbled through t h e solution a t room temperature for 2.5 hr. (efficient stirring). The solvents were removed under vacuum, the solid residue was extracted n-it11 hot ethyl acetate, and t,he solids remaining crystallized from 2-propanol, yielding 150 mg. of pure I X b , m.p. 173-180 and 251-256' (Kofler); [ a ] ~ +81.
