KD16-Ul. Esterification of 2 gave 1, identical with the title compound. Alternatively, 1 was obtained in higher yields by esterification of 21, followed by deprotection of the hydroxy groups. This synthesis gave 1 and 2 from methyl α-D-mannopyranoside in an overall yield of 18 and 20 %, respectively, confirming their absolute configuration.
分别以甲基α-
D-吡喃葡萄糖苷和甲基α-D-甘露
吡喃糖苷直接制备假内酯6和12。所述pseudolactone 6与反应叔丁基lithioacetate,得到保护的,三羟基
环己烯酮羧酸7(51%)。空间位阻,
L-核糖-构型pseudolactone 12与反应
乙基膦酸二
乙酯和
甲基膦酸二甲酯,得到受保护的trihydroxycyclohexenones 17(49%)和18(62%),分别。羟甲基化的
环己烯酮21由18通过先用Me 2 Al
SPh然后再用
甲醛处理,将产物19氧化并消除。21的脱保护得到2,与KD16-U1相同。2的酯化得到1,与标题化合物相同。备选地,通过21的酯化,然后使羟基脱保护,以较高的产率获得1。该合成从甲基α-D-甘露
吡喃糖苷分别得到1和2,总产率分别为18%和20%,证实了它们的绝对构型。