We have been involved in a program to develop new synthetic methods for natural products and pharmaceuticals utilizing a hybrid process in which an enzymatic process and chemical transformations are combined. Optically active bicyclo[3.3.0]octanes should be useful synthetic intermediates for the synthesis of some natural products. Here we wish to report 1) the lipase-mediated demethoxycarbonylation of tetraester 1 to give the enantiomerically pure C_2-symmetric diester (+)-2 or (-)-2 depending on the lipases used, and their synthetic applications to the asymmetric syntheses of iridoids such as (-)-loganin and (+)-nepetalactone, 2) the lipase PS-mediated optical resolution of ketol dl-11a to give ketol (+)-11a and ketoacetate (-)-11b, which were employed for the total synthesis of cis,cis-nepetalactone. 1. Asymmetric Synthesis of C_2-Symmetric Diesters (+)-2 and (-)-2 via Lipase-Mediated Demethoxycarbonylation and the Syntheses of (-)-Loganin and (+)-Nepetalactone. The C_2-symmetric tetraester 1 easily obtained by the one-pot Weiss reaction underwent PPL-mediated demethoxycarbonylation via dynamic kinetic resolution to give an optically active triester (98.3% ee). The triester was demethoxycarbonylated subsequently with Lipase M to afford enantiomerically pure C_2-symmetric diester (+)-2. On the other hand, the same reaction of tetraester 1 with Lipase AY gave directly the enantiomerically pure C_2-symmetric diester (-)-2 having the opposite configurations compared to the reaction with PPL. We demonstrated that the enantiomerically pure diester (+)-2 was useful as a synthetic intermediate for the syntheses of (-)-loganin and (+)-nepetalactone. 2. Lipase PS-Mediated Optical Resolution of Ketol dl-11a and Asymmetric Synthesis of cis,cis-Nepetalactone. The treatment of ketol dl-11a with lipase PS afforded the optically active ketol (+)-11a and ketoacetate (-)-11b in excellent enantioselectivity. Both (+)-11a and (-)-11b were converted to be an intermediate (-)-13 for the total synthesis of cis, cis-nepetalactone.

抄録全体を表示

フラックス残渣の表面にクラックが入ると, 残渣表面の吸湿性が増加する。場合によっては, それが原因になって, その残渣はイオンマイグレーションなどの絶縁劣化を引き起こす。そこで, 著者らはクラックが存在する残渣の表面の吸湿性を定量化する方法について検討を行った。また, 数値化された吸湿性の大きさとイオンマイグレーション発生との関連性を調べ, 吸湿性から残渣の絶縁劣化が予測できるかどうかを検討した。その結果, 表面にクラックが入ったフラックス残渣の表面の吸湿性は, 誘電特性によって定量化できることがわかった。また, 残渣表面の吸湿性を定量化することは, 残渣の絶縁劣化を予測する上で有益な情報をもたらすこともわかった。

抄録全体を表示