72271-67-1Relevant academic research and scientific papers
A novel synthetic method of the (±)-(3aα, 8aα)-ethyl 8β-hydroxy- 6β-methyl-2-oxooctahydro-2H-cyclohepta[b]furan-3α-carboxylate and its chemical transformation
Shimoma,Kusaka,Wada,Azami,Yasunami,Suzuki,Hagiwara,Ando
, p. 920 - 929 (2007/10/03)
The catalytic hydrogenation of ethyl 8-hydroxy-6-methyl-2-oxo-2H- cyclohepta[b]furan-3-carboxylate (6), which was derived regioselectively from 4-methyltropolone (1) in four steps in 62% overall yield, gave (3aα,8aα)- ethyl 8β-hydroxy-6β-methyl-2-oxooctahydro-2H-cylohepta[b]furan-3α- carboxylate (8b) in 45% yield. It is noteworthy that four asymmetric centers newly introduced on the seven-membered ring of 8b were controlled to be syn- oriented by the single operation. The latter was transformed to (3aα,8aα)- 3α,6β-dimethyl-3,3a,4,5,6,8a-hexahydro-2H-cyclohepta[b]furan -2-one (17a) in 77% overall yield in five steps. Reduction of 17a with LiAlH4 gave (±)- 7β-(2-hydroxy-1α-methylethyl)-4β-methyl-2-cyclohepten-1β-ol (22), whose enantioselective acetylation was achieved by vinyl acetate in the presence of Lipase PS to give (+)-7β-(2-acetoxy-1α-methylethyl)-4β-methyl-2- cyclohepten-1β-ol (24) in 48% yield (93% ee) or in 52% yield (77% ee) and (- )-22 in 52% yield (70% ee) or 44% yield (89% ee). Oxidation of (+)-24 with MnO2 gave (-)-7β-(2-acetoxy-1α-methyl ethyl)-4β-methyl-2-cyclohepten-1- one (-)-(25). Similarly, acetylation of (-)-22 followed by oxidation or resulting (-)-24 gave (+)-25.
