COMMUNICATIONS TO THE EDITOR
July 5, 1953
p>() =z() c1
3291
OH
"2
H
114
/
CH3
The presence of the grouping -CH-C-Cin the unsaturated ring of cedrene is well established.2 Raney Ni The size of that unsaturated ring (ring I, fig. 11) has incorrectly been deduced to be five-membered I by previous investigator^^,^^ on the basis of obOH 0 servations which appeared to us to point clearly to a six-membered ring. W e have confirmed our deduction by examination of the infrared spectrum of the anhydride of the bicyclic C13 diacid, norcedrenedicarboxylic acid (NCDA),6 which proved to be that of a glutaric anhydride, with peaks at 5.57 and 5.67 p, while a succinic anhydride, derived from a five-membered ring I, would have absorption maxima at 5.40 and 5.63 p.6 We have further prepared by the action of phenylmagnesium brom" VI1 ide on dimethyl norcedrenedicarboxylate a diVI VI (as the dibenzenesulfonamide) and VI1 (as chenyl lactone, m.p: 173-173.5', which had its barium carbonate) had respectively 51.8 f 1% and infrared band a t 5.70 1,in confirmation of the six43.1 f 1% of the radioactivity of V (as the semi- membered lactone structure corresponding to a carbazone or 2,4-dinitrophenylhydrazone). . In a glutaric acid. The two carboxyls of NCDA are attached to a the corblank degradation of aniline-l-C14 (III),6tg responding percentage activity figures for VI and ring, the size of which we have proved by examinaVI1 were 0.2 f 1 and 96.7 f 1%, respectively. tion of the infrared spectrum of the anhydride of Since in the blank degradation the barium carbon- the monocyclic CII dibasic acid obtained by further ate activity was consistently low, we consider the degradation of NCDAe4 Again this proved to be activity of VI to be the most reliable index of the the anhydride of a glutaric acid and ring I1 is thus established to be five-membered. The posiamount of rearrangement in the amination of I. tion of the gem dimethyl group shown in fig. I1 DEPARTMENT O F CHEMISTRY AND JOHN D. ROBERTS'^ LABORATORY FOR NUCLEAR HOWARD E. SIMMONS, JR. is considered elsewhere.' With respect to ring I11 SCIENCE AND ENGINEERING L. A . CmLsmTn two facts pointed strongly to the arrangement MASSACHUSETTS INSTITUTE OF C. WHEATON VAUGHANindicated in structure 11: The isolation in high TECHNOLOGY, CAMBRIDGE 39, MASS. yield of p-cymene from the catalytic dehydrogenaRECEIVED MARCH12, 1953 tion of cedrene,*.indicating the probable presence (9) Since I was prepared from 111 by Tracerlab, Inc., using the of a potential isopropyl group para to the methyl Sandmeyer reaction, this degradation constitutes a proof of the isotope group of ring I; and the obvious biogenetic relaposition assignment for I. tionship to P-curcumene, of which cedrol is a formal (10) Crellin Laboratory, California Institute of Technology, Pasacyclization product. In any event, this surmise is dena 4, Calif. confirmed by the fact that the dehydroacid obtained from the C11 dibasic a ~ i d ~is9oxidized ~ to THE STRUCTURE OF CEDRENE a,a-dimethylhomotricarballylic acid, an important Sir: result, a possible structural implication of which The tricyclic sesquiterpenes cedrene, ClSH.24, was incorporated, together with previous erroneous and cedrol, C16H260,have been the object, since structural deductions, into the last published their isolation by Walter in 1841,' of a large number proposals for the structure of cedrene.3 The full of chemical investigations2 which have led to the development of the necessarily sketchy outline proposal of no fewer than thirteen different struc- presented here will be given in a subsequent paper.g tures for the tertiary alcohol cedrol and the related CHEMICAL LABORATORIES anhydro compound, cedrene. STORK HARVARD UNIVERSITY GILBERT We have elucidated the structures of these two CAMBRIDGE 38, MASSACHUSETTS sesquiterpenes which can now be represented by I CHANDLER LABORATORY (cedrol) and I1 (cedrene). COLUMBIA UNIVERSITY RONALD BRESLOW HNOi
Hz
NEW YORK 27, NEWYORK RECEIVED JUNE10, 1953
(4). P1. A. Plattner, G. W. Kusserow and H. Kliiui, Hcls. Chim. Acta,
as, 1345 (1942). I
I
CHs
CHs
I
I1
(1) Ph. Walter, Ann., 89, 247 (1841). (2) Reviews of the work in this field up to 1947 are found in J. Simonsen and D. H. R. Barton, The Terpenes, Vol. 111, Cambridge University Press, London (1952); see also S. H. Harper, Ann. Repfs. Chcm. SOC.,44, 143 (1948). (3) The last publiihed propwals are by PI.A. Pluttner, Ckimia, 8, 148 (IQ48).
( 4 4 L. Ruzicka, P1. A. Plattner and G. W. Kusserow, ibid., 36, 85 (1942). (5) P1. A. Plattner and H. Klaui, Hels. Chim. A c f a , 36, 1553 (1943). (6) We have established that the position of the diagnostically more important lower wave length band is not affected by the degree of substitution. (7) G. Stork and R. Breslow, Tms J O U R N ~ 16, , 3292 (1953). (8) W. Treibs, Bcr., 68, 1041 (1985). (9) Structures I and I1 for adrol and cedrene were first presented formally in a lecture given by one of YI st Hsrvsrd on Junusry 17, 1868.
