| Budget Amount *help |
¥2,200,000 (Direct Cost: ¥2,200,000)
Fiscal Year 1995: ¥900,000 (Direct Cost: ¥900,000)
Fiscal Year 1994: ¥1,300,000 (Direct Cost: ¥1,300,000)
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| Research Abstract |
1. Hydroboration-oxidation of 2-methyl-2-propenyl group introduced on carbohydrate skeleton. Methyl 4,6-O-benzylidene-2-deoxy-2-C- (2-methyl-2-prpenyl)-alpha-D-altropyranoside (1a), -idopyranoside (1b), and methyl 5,6-O-cyclohexylidene-3-deoxy-3-C- (2-methyl-2-propenyl)-beta-D-arabinofuranoside (1c) were prepared. A series of dibenzodioxaborepines (2) having bulky substituent groups at the 4,8-positions were also synthesized. Hydroboration-oxidation of the blanched chain sugars 1a and 1b with BH_3・SMe_2 and with 2 gave the corresponding 2-C-[(2-hydroxymethyl) propyl] pyranosides in good to excellent yields where the diastereoselectivity was hardly affected by the bulkiness of the borane reagents used (for 1a ; 7.4-13.0% de and for 1b ; 6.5-13.0% de). In contrast, however, the selectivity of hydroboration of 1c to 3-C-[(2-hydroxymethyl) propyl] furanoside markedly increased with increasing the bulkiness of borane reagents [by BH_3・SMe_2 (in CH_2Cl_2) ; 21% de, by BH_3・SMe_2 (in THF) ; 37% de, by (Sia) _2BH (in ether) ; 33% de, by (Ipc) _2BH (in THF) ; 39-45% de]. When borane reagent 2 having 4,8-di-tert-butyl group was used, the diastereoselectivity was incleased to 62% de.
2. Preparation of C1-C9 fragment of carbomycin B.Hydroboration-oxidation of methyl 5,6-O-cyclohexylidene-2,3-dideoxy-3-C- (2-methyl-2-propenyl)-beta-D-arabinohexofuranoside by the above reaction system, followed by appropriate functional group transformation gave [2S,3R,3 (2R), 5R]-2-formyl-3-(2-methyl-3-pivaloyloxy)-5-methoxyoxolane (3). The reaction of 3 with (Z)-3-[(tert-butyldimethylsiloxy) allyl]-tributyltin and subsequent hydroboration-oxidation afforded the expected product corresponding to the C1-C9 fragment of carbomycin B.However, the configurations at the positions corresponding to the C3 and C4 of carbomycin B have not yet been determined.
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