The total synthesis of (±)-4-demethylaristolone and related compounds

General approach to total synthesis of patchoulane sesquiterpenes

“…In spite of the widespread occurrence of the patchoulanes in nature, evaluation of the odor and flavor properties of these sesquiterpenes has been limited due to the lack of practical synthetic means for attaining working quantities of these compounds. Although syntheses of individual a-patchoulanes have been recorded (Bates and Slagel, 1962b;Büchi et al, 1964;Büchi and MacLeod, 1962;Danishefsky and Dumas, 1968;Hikino et al, 1968c;Piers et al, 1969;Schmalzl and Mirrington, 1970), it was the objective of our work to develop a general synthetic approach which would be adapt- able to all of the sesquiterpenes in this series. Such a general approach is described here.…”

Total synthesis of (±)-aristolone

“…143-144" at 53 mm. The isolated yield of this compound was approximately 22% and thus, in contrast to the equivalent reaction in the model study (5), the direct acid-catalyzed conversion of compound 7 into compound 20 was not particularly efficient.' The n.m.r.…”

“…The structure determination of this interesting natural product was reported (2) some six years later and, in 1962, Biichi and co-workers (3), on the basis of an indirect correlation with maaliol (4), of known absolute configuration, established the absolute configuration of (-1-aristolone as depicted in 1. We previously carried out, and reported in preliminary form (5), a model study involving the synthesis of ( t ) -4 -demethylaristolone. In this paper we describe the total synthesis of (k)-aristolone.…”

Total synthesis, stereochemistry, and lithium–ammonia reduction of (±)-4-demethylaristolone and (±)-5-epi-4-demethylaristolone

“…This synthesis, in which the key step involved the cupric sulfate catalyzed intramolecular cyclization-of the diazoketone 2, was based on a model study involving the preparation of (*)-4-demethylaristolone. The model study, which has already been reported in preliminary form (5), was undertaken primarily with the aim of determining whether or not the crucial cyclization of the type 2 --> 1 would take place. That is, in order to initially avoid some of the stereochemical problems involved in the synthesis of aristolone itself, we first decided to prepare a diazoketone of the type 3.…”