plexes will vary greatly depending on the ratio of iodine to iodide in the complex; moreover, it may be possible to determiiie this ratio quitc unam-
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COMMUNICATIONS To THE EDITOR
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biguously by the method of continuous variations, if a system can be found in which equilihriuin exists. \XES, I O W Z
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COMMUNICATIONS T O 1 H E EDITOR THE STRUCTURE OF DIOSCORINE
tropane (VI). I 2 Similarly the di-p-toluoyl-D-tartrates of IV from cocaine and dioscorine were Dioscorine, C13H1902N, a water-soluble alkaloid, identical. The nuclear magnetic resonance spechas been isolated from Dioscorea hirsuta Blume1s2 trum of dioscorine (in CHC1,) has no peaks above and Dioscorea hispida Dennst.".' The early struc- 1200 C.P.S. l 3 and unactivated methyls are therefore tural investigations2 were continued by Pinder3-9 absent. The configuration a t CZ then was determined : who has proposed three structures, including I, The saturated diol prepared by catalytic reduction for dioscorine. No facts have been presented from which the structure of the nitrogenous nucleus and of I1 had a pK, of 8.81 (Cellosolve) like 2a-hydroxythe location of the lactone ring present in the tropane (VI), pK, 5.42, while @-hydroxytropane alkaloid could be deduced conclusively. In this (1711) had pK, 9.62. The observed differences in communication we wish to present findings which basicity are similar to those of quinine and epiquinineL4and demonstrate that the tertiary hyestablish structure I for dioscorine. in I1 has the n-configuration which is i n droxyl Reduction of the alkaloid with lithium aluminum hydride gave a diol (11),1n.p. 121' (picrate, m.p. .\ 164-165', lit.* 159-160'), which by ozonization was converted to glycolaldehyde and a hydroxyketone (111), m.p. 2 5 O , infrared peaks a t 3540 cm.-' (OH); 1705 cm:-l (C=O); 1405 cm.-' 1 [I Ill (COCH2) and 1360 cm.-l (COCH3) (picrate, m.p. T 120-122'). On exposure to 0.1 N sodium hydroxide, 111 underwent retroaldol cleavage to acetone and a ketone (IV), infrared peak a t 1723 em.-' ( c s 2 ) , 1730 em.-' (Cc14); [o(Iz5D + l i o (c 1.43 in H2O) (di-p-tOlUOyl-D-tartrate, m.p. 149-151 ') , Treatment of IV with ethanedithiol and then de\'Ill sulfurization produced tropane (V), picrate, imp. 250-28s' (dec.) ; chloroplatinate, m.p. 2OS-21O0, identical with authentic samples.lo The ketone IV is therefore tropan-2-one or tropan-6-one. We initially preferred" the 6-substituted structure, agreement with the previously reported infrared (VII), m.p. mainly because of the position of the carbonyl band evidence.* 2P-Hydroxytropane IOo, Y L ~ O D 1.4562 (picrate, n1.p. 263-265') in the infrared of IV. Reduction with sodium borohydride or with hydrogen over Adanis catalyst was prepared by lithium aluminum hydride reducyielded an alcohol (VI), m p . TOo (picrate, m.p. tion of 2P,RP-epoxytropane (IX) (picrate, 1n.p. 262-263'; di-p-tOlUOyl-D-tartrate, m.p. 1G5-1GG0; 248-254') which in turn was available by oxidation di-p-toluoyl-L-tartrate, 1n.p. 1 6 4 7 0.5') which had of tropidine (YIIP with trifluoroperacetic acid in an infrared spectrum entirely different from that of il~etonitri1e.l~The conversion of both cocaine'? and dioscorine to the same tropan-2-one (XI-) il mixture of Ga- and 6p-hydroxytropane, m.p. demonstrates identical absolute configuration16 in 65-81' (cf. ref. 9) prepared by desulfurization of GP-hydroxytropan-3-one thioketal. The three de- the two alkaloids. We are indebted to Eli Lilly and Co. for financial rivatives of the alcohol from dioscorine (I), however, were identical with those of 2a-hydroxy- support and to Prof. E. Schlittler for plant material. I)EPARTMENT OF CHEXISTRY 1) E A \ E R (1) H. W.Schutte, Chcm. Zeiitr., 68, 11, 130 (1897).
Sir :
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(2) M . K. Gorter, Rec. ~ Y U P chim., . 30, 1 6 1 (1911). ( 3 ) A. R. Pinder, Nature, 168, 1090 (1931). (1) A . R. Pinder, J . Chem. Soc.. 2236 (1952i. (5) A. R. Finder, i b i d . , 1825 (1953). (6) A. R. Pinder. %bid., 1577 (1956). (7) A . K. Pinder, Chemistiy und I n i l t r s l v y , 1240 (1957). (8) A. R. Pinder, Telvnhedvon, 1, 301 (1957). ('2) J. B. Jones and A. R. Finder, Chemistry and I n d t ~ s t ~ y1000 ,
(1958). (10) K , Hess, B e y . , 51, 1001 (101s); R. Willstatter and 1'. Iglaiier,
ibid., 33, 1170 (1900). (11) G. Diichi, D. E . Ayer and I?. M. White, XVIth I n t w n . Cvngr. of Pure and Applied Chemistry, Paris, July, 1957.
TECHIYOLOGS c BXITI P. REYNOLDS-WARNIIOFF DIVAIN M LVHITE RECEIVED OCTOBER 6, 1958
?VIASSACHUSETTS 1NSTITUTE O F C A M B R I D G E , ?if~4SSACIICSETTS
(12) 31. R. Bell and d. Archer, accompanying paiier. TVe w i s l i 10 thank n r . S. Archer tor a sumple of this substance. (18) Relatixe to an arbitrarily assigned peak of 1000 c i).s for t h e aromatic proton of toluene. (14) V. Prelog and 0. IIYtiiger, Hf'la. C h i m . A r l t z , 33, '7021 [1931). (15) Method of G. Fodor, J T o t h , I. Koczor, P. Doho and I. Vincie, f h P m i s t y y and I n d u s i v y , 764 (1950). (le) E. Hardegger a n d H. Ott, Hela. Chim. Acta, 38, 312 (195;).
