DAVIDLAVIEAND
1668
hours the dark solution was poured over ice, and the resulting acidic solution was washed with ether, made basic with sodium hydroxide, and heated on n steam-bath overnight. The basic solution was extracted with ether. The ethcreal solution was dried over sodium sulfatc, : ~ n ddry hydrogel] bromide was passed in. T h e precipitate was removed, dissolved in dilute sodium hydroxide solution, and stirrcd overnight with 20 ml. of benzenesulfonyl chloride. The solution was acidified t o p H 1 and the sulfonamide extracted with ether. T h e acidic solution was then made liasic with sotliunl hydroxide, and was extracted with ether. The ether solution was treated with excess methyl iodide, and the precipitated 1,4-methyliminocyclohexanernethirdide (15932 g., 10.7%) had m.p. 279-254". Crystallization from ethanolmethanol gave granular crystals, m . p . 295-295.5' (lit.50 m.p. 299-300'). Anal. Calcd. for C 8 I I d I : C , 37.96; 13, 6.37; N , 5.54. Found: C, 37.87; H, 6.60; K, 5.36. T h e nuclear magnetic resonance spectrum of the methiodide (DaO solvent, methylene chloride standard) had three distinct peaks. T h e peak a t +27 C.P.S. ( a t 40 megacycles) i q assigned to the bridgehead hydrogens, the sharp peak at 4-60.6 C.P.S. is assigned t o the N-methyl hydrogens, and the peak a t +lo0 C.P.S. is assigned t o the methylene hydrog e m . The relative areas under these peaks were, respectively, 2.0, 6.0 and 8.14. MetliyliminocJ.clohexaiie methiodide requires 2.0, 6.0 and 8.0. (50) J V. Rraun and K. Schwarz, A m . , 481, 50 (1930).
[CONTRIBUTION FROM THE
DllvID W I L L N E R
Vol. 82
In order to compare the rate of decomposition of methylcyclohexylcltloroctmine with t h a t of dibutylchloroamine under the same conditions, a 0.327 AT solution of t h e chloroamine in 90'3 sulfuric :wit1 in a quartz flask was irr;itlintetl with u incrcury arc lamp under a stream o f nitrogen. Tlie Iialf-life o f the cliliiroainine w:ts ubont 570 minutes. 1~riidt.r these conditions a 0.28 111 solution of tlibutyleli1~)roanlltlei l l OOyosulfuric acid had a half-life of 10 niinutes. Irradiation of N-Chloroazacyc1oheptane.-S-Chloroazacycloheptane W ~ prepared S from azacycloheptane hy the same procedure described for methylc~-cloIiexylcliloroal~~~~ie. Xpproxiinately 1.X nil. of the chloroamine was dissolved i n 40 i d . of cold 90yc sulfuric acid. Titration of a 1-nil. aliquot showed the solution to be 0.38 M in chloroamine. The solution was irradiated as with rnethylcyclohexylchloroarnirie. The half-life was about 2140 minutes. The solution was diluted with ice-water, made alkaline with sodium hydroxide, and heated on the steam-bath for 6 hours. T h e alkaline solution was then stirred with 5 ml. of benzenesulfonyl chloride for four hours, and extracted with ether. D r y hydrogen brornide was passed into the ether solution, and the inaterial which separated a s a n oily suspension was extracted with water. T h e :iquecius solutiixt waq made alkaline and extractetl with ctlirr. h l c t h y l iodidc was added t o the ethcr solution; the oil wliich separated out (72.0 tng., 3% currectetl for : i l i q ~ o t sri.irioved) coi~ldnot he iiidiicetl t o crystallize.
URBAIZA, ILL.
DANIELSIEFF RESEARCH INSTITUTE,
THE \%'ElZMANN INSTITUTE O F SCIEXCE]
The Constituents of Ecballium elaterium L. X I . Proposed Structures for a-Elaterin and its Degradation Products"2 BY DAVIDLAVIEAND DAVID'IVILLNER RECEIVED AUGUST5 , 1959 a-Elaterin has been identified as a tetracyclic triterpene. A full structure locating all the oxygenated functions is proposed. Structures are also proposed for ecballic acid and other degradation products. The different changes involving the alkaline treatment of welaterin are reviewed.
The oxygen functions of a-elaterin (cucurbitacin investigation is now undertaken to study the difE), the crystalline compound readily obtained from ferent aspects of their action.ll I n view of these the fruit juice of Ecballium elaterizmz, have been properties the full structure proposed for elaterin previously described. 3 , 4 More recently the side in this paper might be of interest in the evaluation chain of this compound has been e l ~ c i d a t e d . ~ -of ~ new drugs for cancer chemotherapy. The present paper deals with the full structure of In previous papers5,6 we have described the elaterin which is one member of a group of com- periodate oxidation of elaterin and the isolation of pounds called cucurbitacinss isolated from dif- trans-4-hydroxy-4-methylpent-2-enoic acid. It was ferent species of the Cucurbitaceae. An inter- therefore proposed that elaterin should have a side relationship has been found among four members of chain similar to elatericin A (cucurbitacin D). this group through a common degradation product However the yields of this acid were very low and interconversion. Elaterin as well as elatericin when compared to those obtained during the oxidaA and B possess anti-tumor activity'o; a biological tion of the side chain of elatericin A. Sublimation of the oily product, obtained from the mother (1) (a) This investigation was supported by a research grant C-2810 liquors of the crystallization of the above acid, ( C 2 ) from t h t National Cancer Institute of t h e National Institutes of Health, Public Health Service: (b) abstracted in part from t h e docyielded a crystalline product which was identitoral dissertation submitted t o T h e Hehrew University of Jerusalem by fied as trans-4-acetoxy-4-methylpent-2-enoic acid David Willnet, ( 2 ) Part X , D. Lavie and Y . Shvo, Tirrs JOVRNAL, 83, 9GG (19GO). (full details will be published by P. R. Enslin).' 'll?
(3) D. Lavie and S. Szinai, ibid., 80, 707 (1958). (4) J. N. T. Gilbert and D. W. LIathieson, Tetrahedron, 4, 302 (1958). ( 5 ) D. Lavie, Y.Shvo and D. Willner, Chumistvy b I n d u s t r y , 1301 (1958).
(6) D. Lavie, Y . Shvo and D. W l l n e r , T H I S J O U R N A L , 81, 3062 (1959). (7) P. R. Enslin and K. B. ?*'orton, Chewirlvy & I n d u s t r y , 1G2 (1959). ( 8 ) P. R. Enslin, S. Rehm and D. E . A liivett, .I. Sri. Pood Agvic., 8,
G73 (1937), and subsequent papers. (9) D. Lavie, Y. Shvo and D. Willner: P. R . En-liii, J. M . Hugo and K . B. Norton, Chemistry & I n d u s t r y , 9.51 (1950).
(10) D. Lavie, D. Willner, 31. Relkin and W. G. Hardy, presented a t t h e Symposium on t h e Chemotherapy of Cancer, Tokyo, October, 1957, Abstracts, p. 53; A C T A , Unio I n t . Contra Cancrum, 15 bis, 177 (1959). Dr. E. Schwenk, T h e Worcester Foundation fur Experimental Biology, Shrewsbury. hlass., kindly informed us t h a t these compounds were found to delay the growth of implanted tumors in t h e cheek pouch of t h e hamster. (11) We thank the h'ational Cancer Institute of the National Institutes of Health, Public Health Service, for a n additional research grant C-2810 (C3S) supporting the bioloeical aspects of this investigation. A full report will be published elsewhere. ( 1 2 ) D. Lavie and Y.S h v ~ i C , h m z s i r y cc' Induslry, 420 (1059).
~ T R U C T U R EAXD DEGR,ID.\TION PRODUCTS OF ~ - E L . ~ T E R I X
April 3, I X i O
1GGS
These evidences pointcd toward the location of the one acylatable hydroxyl was detected earlier duracetic acid ester group of elaterin in the side chain ing the acetylation of elaterin (elaterin diacetate) . 3 , 4 as shown in I. From earlier acetylation experi- The nature of the last oxygen atom in elaterin was ments with elaterin and elateridir~,~ the tertiary now found through a careful study of the infrared nature of this ester has already been suggested. spectrum in the carbonyl region. I n order to obOf the eight oxygen atoms of elaterin (I), C32H4408, tain better resolution, a calcium fluoride prism Four are therefore to be placed in the side chain.G,13 was used, and the 16S3 cm.-' frequency previously In acetic acid solution, using platinum as catalyst, reported3 was resolved to its two components. dihydroelaterin was easily obtained. The hydrogen- The four carbonyl absorptions, which were now ation had to be discontinued when one mole of hydro- observed were identified as follows: 1724 ester, gen was absorbed. The ultraviolet spectrum of the 1694 hindered ketone, 1688 a,@-unsaturated keresulting crystalline product had no maximum a t tone and 1660 cm.-l for the diosphenol. The 1694 234 mp, and it was deduced that the double bond cm.-' frequency is rather low for a saturated conjugated to the ketone in the side chain of elaterin ketone, but is in agreement with observations made was reduced during this process. on ketones in a hindered p0siti0n.l~ It could not, however, account for a second a,p-unsaturated 0 ketone in the molecule, inasmuch as the ultra0 , violet spectrum of dihydroelaterin (see above) did not have any absorption in a position required (! P. F . for such a system. This hindered ketone accounts therefore, for the eighth oxygen atom not yet identified in the molecule of elaterin.13 The unreactive nature of this ketone was already observed during reduction experiments made on this comIIa, R = H pound; only boiling for a long time with lithium 11. R = C H , aluminum hydride did reduce it.3 I n agreement with our results, Gilbert and Mathieson4 observed 0 5, that ecballic acid formed a bis-2,4-dinitrophenylhydrazone thereby characterizing this group. Thus, summing up the carbonyl functions of elaterin (I), two are in the side chain forming an a,@-unsaturatedketone and the acetic ester group, the diosphenol system is in a six-membered r i n g 3 while in addition there is a sluggishly reactive CH, CII, ketone, probably in a hindered position. I At this stage the study of the dehydrogenation of elaterin (I) was undertaken. For this purpose dihydroelaterin was reduced with lithium aluminum hydride (no carbonyl absorption recorded in CHTO the infrared), and the amorphous acetylated prod0 C =c c-c uct was treated with selenium powder. Among the products of the dehydrogenation, 1,2,8'I' 1'I trimethylphenanthrene was isolated and purified CII, C" through its trinitrobenzoate adduct. It was identified by the ultraviolet spectrum, and by a mixed melting point with an authentic sample of the adduct, no depression being observed. A second unidentified degradation product forming a 1,3,5ck! ,ooc . trinitrobenzoate adduct, m.p. 175-178', was also isolated. The ultraviolet spectrum of this product indicated a tetrasubstituted phenanthrene. EnVI1 VI11 slin and Rivett 15a have reported the isolation of similar dehydrogenation products from cucurCHJ bitacin A ; insofar as the dehydrogenation of tetracyclic triterpenoids has been investigated, they have furnished as main product 1,2,S-trimethylphenanthrene.lKb I n view of these findings, and c H,OOC considering the nature of the side chain, it can be assumed as already suggested by these authorslB HO that elaterin has a tetracyclic triterpenoid struc-
i
@ , IX
I n addition to the four oxygen atoms already placed in the side-chain of elaterin (I), two are involved in the diosphenol of the ring system and (13) D. Lavie and D. Willner, Proc. Chcm. Soc., 101 (1959).
(14) A. R . H. Cole and D. W. Thornton, J . C ~ P V Soc., I. 1007 (1956); 6. also ref. 20a. (15) (a) P. R. Enslin and D. E. A . Rivett, J . Chein. SOC.,3682 (1956); (b) E . I
