Optically active methyl deoxypodocarpate ((S) (+)-5b), 92% optically pure, was synthesized from (R) (+)-δ-ketoaldehyde ((R) (-)-3a) which was obtainable by the asymmetric synthesis using D-proline-derived pyrrolidine ((R)-4 (R2=CH2NC4H3)) as a chiral additive. The chemical scheme which was previously developed, was used for the conversion of (R) (-)-3a to (S) (+)-phenanthrone derivative ((S) (+)-1a), and a combination of reductive carbomethoxylation and reductive alkylation was adopted for preparing (S) (+)-5b from (S) (+)-1a. Since (S) (+)-5b had already been converted to naturally occurring podocarpic acid ((S) (+)-5a), the asymmetric synthesis of (S) (+)-5a was accomplished.
以(R)(+)-δ-酮醛((R)(-)-3a)为原料合成了具有光学活性的脱氧十二
碳酸甲酯((S)(+)-5b),其光学纯度为92%。之前开发的
化学方案用于将(R) (-)-3a 转化为(S) (+)-phenanthrone 衍
生物 ((S)(+)-1a),并采用还原性碳甲氧基化和还原性烷基化相结合的方法,从(S) (+)-1a 制备 (S) (+)-5b 。由于(S) (+)-5b 已经转化为天然存在的荚果酸((S) (+)-5a ),因此(S) (+)-5a 的不对称合成得以完成。