Takushi Kurihara

Synthesis of strained 8-membered heterocyclic allenes by [3,3] sigmatropic rearrangement and their reactivities

A new type of 8-membered heterocyclic allenes were synthesized by the [3,3] sigmatropic ring expansion of 6-membered cyclic thionocarbonates. The MNDO optimized structure indicated the allenyl moiety in cyclic allene (3) is bent and strained. Reactivities of the heterocyclic allenes were also examined

Chemistry of ethyl 2-{[t-butoxycarbonyl(methyl)amino]methyl}-3-hydroxy-3-phenyl(or 3-vinyl)propionate : mechanistic considerations in the formation of tetrahydro-1,3-oxazin-2-ones

The threo- and erythro-selective aldol condensation of ethyl 3-[t-butoxycarbonyl(methyl)amino]- propionate with benzaldehyde gave the benzylic alcohol-substituted aminopropionate ethyl 2-{[t-butoxycarbonyl(methyl)amino]methyl}-3-hydroxy-3-phenylpropionate as a diastereoisomeric mixture. On treatment with methanesulphonyl chloride and triethylamine, the threo-isomer was converted into ethyl 3-methyl-2-oxo-6-phenyl-3,4,5,6-tetrahydro-2H-1,3-oxazine-5-carboxylate, and the erythro-isomer gave simply its corresponding mesate derivative. The mechanism for this transformation is discussed.

Synthesis of cis- or trans-2,4-Disubstituted Tetrahydrofurans Bearing Amino and Imidazole Groups by Efficient Use of the Modified or Standard Mitsunobu Cyclization: Synthetic Studies toward Novel Histamine H3-Ligands

R,4S) or (2S,4S)-4-Aminotetrahydrofuran-2-yl)imidazole ((-)-1a or (-)-1b) and its enantiomers ((+)-2a and (+)-2b) were synthesized by efficient use of the modified or standard Mitsunobu cyclization.