Kimiko Kobayashi

Potent inhibition of macrophomate synthase by reaction intermediate analogs.

Potent inhibitors for macrophomate synthase, which has recently been found to catalyze a highly unusual five-step chemical transformation, were explored. Among 11 oxalacetate analogs tested, only three analogs had moderate to relatively strong inhibitory activities (I 50 1.3-8.1 mM). On the other hand, among 35 bicyclic intermediate analogs synthesized, two diacids were found to be the most potent inhibitors (I 50 0.80, 0.84 mM) which had a much higher affinity than that of the natural substrate 2-pyrone. (-)-Enantiomers of the diacids showed 30 times stronger activity (I 50 0.34, 0.41 mM) than (+)-ones. The I 50/K m values (0.20, 0.24) showed their potent inhibitions. Competitive inhibitions were observed in two representative inhibitors.

Studies on the constituents of aconitum species. VII: On the components of Aconitum japonicum Thunb.

Two new diterpenoid alkaloids, subcumine and subcusine, were isolated from the roots of Aconitum japonicum Thunb. The structures of these alkaloids were determined on the basis of spectral data, chemical evidence, and X-ray analysis. We also have isolated two known alkaloids, ezochasmaconitine and anisoezochasmaconitine

Asymmetric hetero Diels-Alder reaction of homochiral thiabutadienes, 3-(arylmethylene)thiocamphors

Abstract The highly diastereoselective hetero Diels-Alder reactions of homochiral camphor-derived thiabutadienes to afford novel, optically active bornene ring-fused dihydrothiopyrans are described.

Highly regio- and stereoselective reductions of spiroketals

Abstract Highly regio- and stereoselective reductions of the spiroketals have been achieved by DIBAH and silane-Lewis acid. The key factors of these selectivities were attributed to steric hindrance of α-methyl group at spiroketal and to vicinal ether oxygens for bidentate chelation.