Masami Okabe

A cyclopropano analog of 2′,3′-dideoxycytidine: stereoselective formation of a [3,1,0] bicyclic system via homologous ferrier reaction

Abstract A synthesis of 2′,3′-α-methylene-2′,3′-dideoxycytidine is described in which the [3,1,0] bicyclic system and the glycosidic linkage were constructed simultaneously.

Improved synthesis of 2-amino-5-chlorophenyl-2′-pyrrylketone, a key intermediate in the synthesis of HIV Tat-antagonists

Abstract The reaction of a 2-phenylbenzoxazinone with pyrryl Grignard reagent is very efficient compared with that of a 2-methylbenzoxazinone. The title compound was prepared from 5-chloroanthranilic acid via the 2-phenylbenzoxazinone in 92% overall yield. This method was also successfully applied to the synthesis of 2-aminobenzophenones.

Effects of trialkylsilyl protecting groups on the photolysis of 1α-hydroxy-provitamin D3

Abstract The quantum yield of the photolytic opening of the diene ring of a 1α-hydroxyprovitamin D 3 analog decreased with an increase in the size of the trialkylsilyl group on the 1α-hydroxy group. When the 1α-hydroxy group was protected as a triisopropylsilyl ether ( 4c ), the quantum yield of the photochemical ring-opening reaction was found to be about one-third of that of the parent compound ( 5 ).

An efficient synthesis of (22E,25R)-1α,25,26-trihydroxy-Δ22-Vitamin D3

The title compound 2 was prepared from C22-aldehyde 3 in 51% overall yield. The key feature of this synthesis is a one-pot construction of the requisite side chain using a-lithiomethylenetriphenylphosphorane 4 and commercially available (S)-2-methylglycidol.

Effects of protecting groups on the previtamin D/vitamin D equilibrium

Abstract The previtamin D-vitamin D equilibrium shifts toward the previtamin side with an increase in the electron-withdrawing ability of the protecting group on the 3-hydroxy group.

Aminotransferase catalysis applied to the synthesis of a PAF antagonist

(R)-alpha-Methyl-3-pyridinebutanamine (5) was required as a key intermediate for production of the PAF antagonist [(R)-(E,E)-5-(4-methoxyphenyl)-N-1- methyl-4-(3-pyridinyl)butyl-2,4-decadienamide (1). A method meeting the requirements of technical simplicity and economic viability was developed using an aminotransferase ex. B. megaterium to catalyze a kinetic resolution of racemic alpha-methyl-3-pyridinebutanamine (3). 5-(3-Pyridinyl)-2-pentanone (4) produced from the (S)-enantiomer, with co-generation of alanine, is recycled by catalytic reductive amination.