The vinylalumination of α-substituted aldehydes gave anti- and syn-adducts with moderate diastereoselectivity. The diastereomeric ratio was inverted by the addition of lithium or sodium perchlorates. Thus, both anti- and syn-adducts were isolated and transformed into the biologically active conduritols, pericosine B and C, respectively. Formal synthesis of pericosine A was achieved with the anti-adduct. The rationales for the different diastereoselectivity are discussed.
α-取代醛的
乙烯基氨化反应可产生具有中等非对映选择性的反加成物和合成加成物。加入
高氯酸锂或
高氯酸钠后,非对映比率发生了逆转。因此,反加成物和合成加成物都被分离出来,并分别转化为具有
生物活性的缩
脲苷--包尿
嘧啶 B 和 C。高果苷 A 的正式合成是通过抗加成物实现的。本文讨论了非对映选择性不同的原因。