8/12/2019 0012-0015

1/4

Tetrahedron etters, o, 7, pp. X2-15, 959. ergamon ress Ltd. Printed inGreat Britain.

Organic Chemistry epartment, ndian Institute f Science, Rangalore(Reoelved June 1959)

VARIOUS structures I,1 II,* III,5 I+> h ve been proposed for humulene.While the nature of the carbon-skeleton s well established,5 he positionof the ethylene linkages s not known with any certainty, ecently, ehave demonstrated6 hat the closely related sesquiterpene etone,zerumbone,ha8 the structure (V), We have now examined the proton magnetic resonance(PMRf spectra of humulene zerumbone nd their hy~oderivatives, and thedata permit us to assign unequivocally he structure (IV) to humulene.The PMR speatrum* f zerumbone ad peaks (all well-resolved) t 147.7

F. Sorm, b, treibl, 3. Pliva snd P. Herout, Coil, Czech. C&em,Coz=, ii, 639 (1951).G. R. Clemo and J. 0. Harris, Ohem & Ind 799 (195l)g , W Fawcettand J. 0. Harris, Ibid, 18 (lgm. Sac, 2675 (1954).Sukh Rev, Curr. Soi, 22, 296 (1951).P. Clarke and 0. R. Ramage, J. Chem. Soo, 4354 (1954).F, Sorm et al,, Coil, Gzeoh, Chem. Comm. 22, 570 (1954).Sukh Rev, Chem. & Ind, 1051 (1956).The spectra were determined t 40 mc o 2 solutions n carbontetrachloride, ith a Varian Model V-43003 igh resolution pectro-photometer. he chemical shifts were measured relative to water.The assignments or zerumbone re confirmed y the PMR spectra oftetrahydroserumbone,exahydrozerumbone, nd humulane.

12

8/12/2019 0012-0015

2/4

Structure f humulene 13(two E-dimethyl groups), 132.7 (one CH~~=~-gro~p protons),124.8 (second CElrFQ 4, 104.3 (and m n o r peake at 110.6 nd 115.3counts/set; hree-C groups proton@), -14.2 a triplet; ne olefinioproton), and -37.9 countsfsec (two olefinic ydrogen6 @ to the carbonyland one olefinia proton a to the aarbonyl). It should be noted here thatthe 'saturated' ethyl groups, 'olefinia' ethyl groups end the methylene

\ \g \

Ip

groups are well-separated n ahumuleneu is almost identicalmethylene proton region [peaks

acharacteristic anner, he PM? spectrum ofwith that of zerumbone n the methyl andat 152, 137.8, 128.8, and 113.2 (with a

small peak at 122.2) counts/sea ith the areas approximately n the ratios2:1:1:2]and this would indicate that humulene also hae four methyl ETOUW,which is in accord with structure (IV) only. Besides these bands, humuleneshowed the remaining 'extra' ethylene group at position 9, ae expected,at a still lower field strength (peaks at 90.8 and 98.6 aounts/eea ith

* These protons are well-eeparated rom the =C-CH peaka by virtueof all the methylene group8 being allylic to thejethylenio inkages,** Humulene as isolated fro&the essential ail of Z s;zbet5,fter precise fractionation ad; b.p, ll4-1150 5 mm, II7

-0.31, nitrosoahloride .p. 175-176'~ rioxide .p, 122O:

8/12/2019 0012-0015

3/4

14 Struoturo of humulene

the areas approximately in the ratio I t1 and roughly of one-third theinteneity of a single methyl peak); the olefinio protons showed up aa aoomplex group of bandz, the major peaks being located at -1.0, -16.8, nd-24.6 ounte/seo.

Aooording to previous workers , humulene oontains one exo-oyolio =CR2group, and this contention is based on the infra-red data,7 and =CH2 groupdeterminations involving ozonolysls.l Since, ozonolysie of oertain ayatemeIs known to yield abnormal products, the reeulte of CR2 group estimationsdo not constitute an argument e&net etructure (IV). Ae for the infra-reddata, we have re-examined the infra-red absorption of humulene quantita-tively, and find the apparent e of the relevant peaks ae follower1665 6 20.8), 965 ( C 125)) 885 ( 6 32), end 820 cm ( f 64). I t would be

-1clear from this data that the peak at 885 cm , on which the presence of=CR2 group had been baaed by these workers, ie very weak,* and hence iznot a forcing argument for the presence of -=(X2 group. Thus, the evidence .presented in this paper allows the unequivocal formulation of humuleneas (IV), This structure Is directly related to that of zerumbone by anoxidation-reduction system, and we are aurrently trying to effeot suchtranaf ormationa.

7 F. Sorm, J . Mleziva, 2. Arnold, and J . Pl iva, Call. Czech. Chem,Cozz% &a, 699 (1949).

* The neual value of the apparent ( for vC=CH2 ieb% -115. The intensities of the other bands~~09~(~~ trano--I iT = X-) and 820 am-l (two -HF-C-) are ae antioipated.(R. IV. J ones and C. Sandorfy in A. Weiaebergere Technique ofr~ani Chemistry Vol. IX, pp. 367-384. Intersoienoe, Wew York(1956).

8/12/2019 0012-0015

4/4

Structure of humulene 15A fuller aaount of this work xl11 be reported shortly in Tetrahedron.

A&norledgement - This work was aarriea out at the IVoyes hemicalLaboratory, niversity of Illinois, rbana, and the author wishes toplaoe on record his ainaere gratitude to Professor . J. Corey forthese facilities.