Terrahukoa Vat. 48. No. 25. pa. 5265-5272 1992 v $5.00+.00 RintsdinGrutBriti 01992Fk!rgMmnPrusLtd Synthesis of ( + )-Isoalantolactone and ( + )-Isoalloalantolactone from (-)-Santonin Gonzalo Blay, Luz Cardona, Begofia Garcia, Jost R. Pedro* and Angel Serrano Departament de Qufmica Orgkxka, Facuitat de Qufmica, Uoivcrsital de Val&Ga, 46100-Burjassot (Vakncia) Spain. (Received in UK 23 April 1992) Key Words Santonin, Isoalantolactone; Isoalloalantolactoae; Synthesis; Functionality Transfer. Abstract. This paper reports on the chemical conversion of (-)-santonia into (+)-koalantolactone and (+)-isoalloalantolactone involving funuionality transfer from Qi to Cs, refunctionalization of the ring A and the formation of the cr-methylened 612-elide moietv. Isoalantolactone zyxwvutsrqponmlkjihgfedcbaZYXWVUTSRQPONMLKJIHGFEDCBA (1) and isoalloalantolactone (2) are two members of the eudesmane class of sesquiterpenes with an a-methylene+actone moiety.’ These compounds have considerable biological activities as allergenic2 and cytotoxic3 agents, inhibitors of plant germination4, antifungal,5 nematocida16 and feeding deterrent activity against pest insects7 Isoalantalactone (1) is a metabolite very characteristic of In&u species.’ of which several synthesis of racemic form are reported.’ On the other hand, isoalloalantolactone (2) was first found by Kalsi et al. from hula racernma9 and afterwards by Bohlmann et al. from Artemisiu iwayomogi.10 Isoallolalantolactone (2) was obtained as a secondary product in a synthesis of I-deoxyivangustin from artemisin.” As part of our current synthetic program related to natural sesquiterpene lactones with biological activity, we now report the successful transformation of santonin (3) into the two above mentioned lactones (1) and (2). RESULTS AND DISCUSSlON For the purpose of the synthesis of 8,12-lactonized eudesmanolides 1 and 2, introduction of an oxygen function at the Cs position of santonin is necessary. Recently12 we have reported a functionality transfer from G to Cs in santonin, which includes the preparation of the trienone 4 and subsequent allylic oxidation to give 5. Once the oxygen function was transferred from Ck to Cs, the product 5 was 5265