Katsumasa Harada

Enantioselective addition Of diketene to aldehydes promoted by chiral schiff base—titanium alkoxide complex. Application to asymmetric synthesis of potential inhibitors of HMG coenzyme reductase†

Highly enantioselective addition of diketene to aldehydes was achieved by using novel Schiff base-titanium alkoxide complexes. Up to 92% ee of 5-hydroxy-3-oxoesters was obtained. This procedure provides an efficient method for the asymmetric synthesis of potential inhibitors of HMG coenzyme reductase.

Syntheses of trans- and cis-3-methoxy-4-methylthio-2-piperidinethiones previously proposed for raphanusanins ; correct structures of raphanusanins

Trans- and cis-3-methoxy-4-methylthio-2-piperidinethiones previously proposed for raphanusanins as a light-induced growth inhibitor, have been synthesized starting from the known α,β-unsaturated lactam. However, the spectral data of the synthetic compounds are incompatible with those of natural ones. Thus, reexamination of 1H and 13C NMR spectra of the natural samples has led to correct structures for raphanusanins. The synthetic compounds also show a growth inhibitory activity.