62
Journal of Natural Proa'ncts Vol. 49, No. I , pp. 62-66,Jan-Feb I986
STUDIES ON REARRANGEMENTS IN DERIVATIVES OF GRANDIFLORENIC ACID, PART 2 . SYNTHESIS OF METHYL (-)-~~-NORKAUR-~CY-METHYL-~( lo), 16-DIEN-lg-OATE, A NEW TETRACYCLIC ROSANE-TYPE DITERPENE TATSUHIKO N A K A N Oand , ~ ALFONSO MARTIN, Centro de Quimica, lnstituto Vmezolanode lnvestigaciones Cimtifias (IVIC), Apart& 1827, Caracas 1010-A, Venezuela and ALFREW USUBILLAGA lnstituto de Invactigacidn Quimica, Facultadde Farmacia, Universidad de Los Andes, Apartado 143, Mirida, Venezuela AssTmff.-The synthesis of the title compound (k), a new tetracyclic rosane-type diterpene, from grandiflorenic acid (IC),is described.
In Part 1of this series ( l), we have reported on the rearrangement of the epoxides of dihydrograndiflorenic acid (la)I( -)-kaur-9( 11)-en- 19-oic acid] and its methyl ester (Ib).In this case, the epoxidation of compounds la and lb yielded the a-epoxide. Hence, upon cleavage of these epoxides with boron trifluoride-Et,O complex, the C(8)C( 15) bond rather than the C(20)-methyl group migrated to C(9), resulting in the formation of compounds 2a and 2b, respectively. Because transformation of grandiflorenic acid (IC)to the analogues of zoapatlin (3a)(2), eupatalbin (3b),or eupatoralH
1 a
RI=
H , R Z = ( ~Ma
2
a
b R 1 = Me , R2=
