Koji Asai

Synthesis of cyclopentano[c]-s -triazoles by the intramolecular ring transformation of 1,3,4-oxadiazoles

Cyclopentano[c]-s-triazoles were synthesized by intramolecular ring transformation starting from y-keto-l,3,4-oxadiazoles 5 and 9. The required functionality for this intramolecular reaction was established by (i) the reaction of lithiated 2-methyl-l,3,4-oxadiazole 4 with the methyl enol ether of α-bromo ketones followed by hydrolysis; (ii) reductive amination of γ-ketones 5 and 9 to further reorganized hydrazide 7 and y-amino-l,3,4-oxadiazole 9 with NaBH3CN; and (iii) pyrolysis of 7 and γ at 280° (5 mmHg) to the cyclopentano[c]-s-triazoles 8 and 11. By the same treatment, the S-connected analogue 2 afforded the desired fused s-triazole 17.

A novel route to the 2-aza-adamantyl system via photochemical ring contraction of epoxy 4-azahomoadamantanes

Epoxy 4-azahomoadamantanes rearranged to give, on photolysis, N-acyl-substituted 2-aza-adamantanes as the only products.

Enantioselective synthesis of the carbapenem ring system from (S)-proline

Enantioselective synthesis of (+)-PS-5 via stereoselective alkylation of proline derivatives is described.

Synthesis of 8,9,10,11,12,13,13a,14-octahydro-7,11; 9,13-dimethanoazonino[1,2-b]isoquinolin-5(7H)-ones and some related derivatives by photocyclization reactions of 5-methylene-4-aroyl- and -acryloyl-4- azatricyclo[4.3.1.13,8]undecanes (4-azahomoadamantanes)

5-Methylene-4-aroyl- and -acryloyl-4-azatricyclo[4.3.1.13,8]undecanes (2a–h) have been prepared by acylation of 5-methyl-4-azatricyclo[4.3.1.13,8]undec-4-ene (1). Irradiation of 4-aroyl derivatives (2a–d) afforded 2- or 4-substituted 8,9,10,11,12,13,13a,14-octahydro-7,11; 9,13-dimethanoazonino[1,2-b]isoquinolin-5(7H)-ones (3a–d) in good yields via enamide photocyclization. DDQ oxidation of (3a–d) gave the corresponding hexahydroisoquinolin-5(7H)-ones (4a–d). Among the acryloyl derivatives, only the methacryloyl derivative (2g) afforded the enamide photocyclization product (5) in a lower yield, the other acryloyl derivatives (2e,f,h) when irradiated yielding the corresponding vinylogous amide derivatives (6a–c)via a 1,3-acyl shift.