3062
DAVIDLAVIE,YIOUVXL SHVU A N D DAVID\I'ILLNEK ICUh I ' K I B U I ' I U N
PKUM TtlE U A X I S L SIEPF
RESEAKCII 1hS'I'ITUI'S,
The Constituents of Ecballium elaferium L. VII. cr-Ela terin','
Vol. SI
THE W E I Z M A X h I N S r I T U l E O F S C I E N C E ]
A Side Chain of Elatericin A and
BY DAVIDLAVIE,\ 7 0 r ; v x ~SHVO AKD DAVID WILISER RECEIVED DECEMBER 15, 1958 During degradation studies on elatericin X and welaterin, trens-4-hydroxy-4-methylpent-Z-enoic acid has been obtained, thereby elucidating a side chain in these compounds. Seven carbon atoms and three oxygen atoms have been identified in this side chain.
I n previous papers2s'iof this series the functions products melted at So,and a mixture of the two present in elatericin A and welaterin were described. compounds did not depress t h e melting point. During this investigation elatericin A was oxidized Moreover, the infrared spectrum of both comwith periodic acid, and two moles of this reagent pounds were superitnposable throughout the whole was c o n ~ u m e d . ~The aqueous layer which re- range. mained after t h e filtration of t h e amorphous oxiCH: H dation product, containing the bulk uf the molecule, I ' was continuously extracted with ether. By treat- HOC-- C-CC0.H + I I ing the ether residue with chloroform, a crystalline CH: H water-soluble acid was obtained. This compound, I 111.p. 102-103O, which analyzed for CsHloOa, CIL, CII, was identified as trans-4-hydroxy-4-methylpent-2cII ,/y-C112 enoic acid ( I ) , not described heretofore, on t h e c) cli2f- HOCC=CO.II following grounds. The ultraviolet spectrum of I ' co / CH3 this acid, Xmax 208 mp ( E 9,500), pointed out in a clear way t h a t a double bond was a,p-conjugated I1 I11 to the carboxylic acid group.5 This was also seen II in the infrared spectrum, vmaX 1703, 1651 and 980 I I€,C c co crn.-l, the last frequency indicating the trans I OH configuration of the double bond.6 Three carbon H O C c c I? l i ' ----+ atoms including the carboxylic group were thereby Cllj 11 0 1I defined. The remaining half of the molecule should also acconimodate a hydroxyl group indicated by a I\ lIjC 0 l1,C c11, I ' I ' 1)road hand in the hydroxyl region. HydrogenaHOC CII + CII,COCKK' COCHOI1 tion of the double bond over platinum yielded a I I tiistillable oil which showed a band at 1778 C I ~ . - ~ \ CIIj OH \1 in the infrared attributed t o a five-menibered lacAcid I, obtained by the periodic acid oxidation tone (11) thus locating the hydroxyl group a t the -/-position. Of the two possible structures to be of elatericin A, was therefore originated from a side considered for the molecule, a straight chain of chain having structure 117. Oxidation of welaterin with periodic acid, folcarbon atoms or a branched chain having a gcmtliinethyl group on carbon atom four, the optical lowing the same sequence of experiments, yielded inactivity of the coinpound pointed only toward also acid I identifying the same side chain (IV) the second structure (I), which was confirmed by for this compound. I t has been found by Iiivett synthesis. 4-Hydroxy-4-niethylpent-2-ynoic acid .md Herbsteinlo that during the treatment of a(111) was prepared by treating the Grignard re- elaterin with hot alkali, a reaction already investigated for the preparation of ecballic acid," acetoin action product of but-3-methyl-3-hydroxy-l-yne with carbon d i ~ x i d e . ~Repeated attempts to was formed. Acetoin was obtained as the 2,4obtain I by reducing stereospecifically the pentynoic dinitrophenylhydrazone of biacetyl, following stem1 acid I11 with sodium in liquid ammonia* were un- distillation of the alkaline reaction mixture. Resuccessful ; the acid I11 was therefore hydrogenated peating this experiment with elatericin A resulted over platinurn and the product obtained was iso- also in the formation of acetoin. The reaction caprolactone (II).9 Both synthetic and degraded product from welaterin, iianiely ecballic acid, as well as t h e corresponding amorphous acid ob(1) This investigation was supported b y a research grant CYtained froin elatericill *\, contained a methyl 28lO(C) from the Xatiiinal Cancer Institute of the Sational Institutes ketone indicated by an iodoform test. Iik-ett S); (IJ) P. I
