Hydrogen bonds as presented in Figure 2 cannot account for the enantioselective attack of cob(I)alamin (4(I)) or heptamethyl cob(I)yrinate (5(I)) on one of the two enantiotopic faces of the substrates. The attack of the strongly nucleophilic 3d orbital is preferentially directed to the re-side of the starting materials with (Z)-configuration and leads, after the highly stereoselective reductive cleavage
如图2所示的氢键不能解释在基质的两个对映体表面之一上的Cob (I)alamin(4(I))或庚甲基
水合Cob(I)yrinate(5(I))的对映选择性攻击。的强亲核3的攻击d轨道被优先引导到重新起始原料侧的与(Ž) -构型和导线,将Co,C键的高立体选择性还原裂解后,以饱和的产品(小号) -不同对映体过量的-构型(参见方案1、3和表1)。