中文名称 | 英文名称 | CAS号 | 化学式 | 分子量 |
---|---|---|---|---|
—— | 3-<(tert-butyldimethylsilyl)oxy>-4,5-dimethoxybenzyl alcohol | 111394-55-9 | C15H26O4Si | 298.455 |
—— | 3-tert-butyldimethylsilyloxy-4,5-dimethoxybenzyl bromide | 111394-56-0 | C15H25BrO3Si | 361.351 |
—— | 3,3'-bis-(tert-butyldimethylsilyloxy)-4',4,5-trimethoxy-(E)-stilbene | 111394-59-3 | C29H46O5Si2 | 530.852 |
Further investigation of the South African tree Combretumcaffrum (Combretaceae) for murine P388 lymphocytic leukemia (PS) cell-growth inhibitory substances has led to discovery of three new active constituents designated combretastatins A-2 (5a, PS ED50 0.027 μg/mL), A-3 (5b, PS ED50 0.026 μg/mL), and B-2 (3b, PS ED50 0.32 μg/mL). Both combretastatins A-2 and A-3 were found to markedly inhibit tubulin polymerization. The structure of each combretastatin was firmly established by a combination of high resolution (400 MHz) 1H and 13C nuclear magnetic resonance and mass spectral analyses followed by total syntheses. The conversion of methyl gallate (7b) to combretastatin A-2 via intermediates 7c → 7d → 7e → 7a and 6a → 5a illustrates the practical synthetic route utilized for obtaining these substances. The Wittig reaction employed as the penultimate step in obtaining combretastatins A-3, afforded predominantly the natural Z isomer.