Total synthesis of (±) maculalactone A, maculalactone B and maculalactone C and the determination of the absolute configuration of natural (+) maculalactone A by asymmetric synthesis
作者:Geoffrey D Brown、Ho-Fai Wong
DOI:10.1016/j.tet.2004.04.060
日期:2004.6
inexpensive starting materials. Maculalactones B and C were synthesized by a minor modification to this procedure, and the synthetic design also permitted an asymmetric synthesis of maculalactone A to be achieved in around 85% ee. The (+) and (−) enantiomers of maculalactone A were assigned, respectively, to the S and R configurations on the basis of the chiral selectivity expected for catecholborane reduction
来自海洋蓝细菌Kyrtuthrix maculans的Maculalactones A,B和C是仅有的基于自然界已知的三苄基丁内酯骨架的化合物,而来自自然资源的(+)Maculalactone A具有对各种海洋食草动物和海洋定居者的显着生物学活性。现在,我们从便宜的起始原料开始,通过五个步骤进行了外消旋黄酮内酯A的简捷合成。通过对该程序进行较小的修改,合成了黄酮内酯B和C,并且合成设计还允许在约85%ee中实现黄酮内酯A的不对称合成。Maculalactone A的(+)和(-)对映体分别分配给S和R根据在Corey's恶唑硼烷催化剂的存在下儿茶酚硼烷还原不对称酮的预期手性选择性进行构型。令人惊奇,似乎自然(+)maculalactone A被生物合成在K. maculans在部分外消旋形式,包含约 (S)对映体的90–95%和(R)对映体的5–10%。因此,巧合的是,从不对称合成获得的产