The Development of Enantioselective Cyanohydrin Synthesis by Artificial Enzyme.

以环状二肽为催化剂，通过氰化氢与醛的加成反应，实现了氰醇的不对称合成。以苯甲醛为底物，由S-苯丙氨酸和S-组氨酸两个氨基酸残基组成的环状二肽环-（苯丙氨酰-S-组氨酸基）得到光学活性的扁桃腈，其对映体过量（ee）为97%，化学产率为97%。扁桃腈的立体化学产物为R。另一方面，当环-（S-亮氨酰基-S-组氨酰基）用作催化剂以得到S-氰醇时，观察到立体化学偏好的反转。因此，通过选择环状二肽中的氨基酸残基，建立了两种对映体的氰醇合成方法。此外，α，β-不饱和醛与环-（S-苯丙氨酰-S-组氨酰）和环-（S-亮氨酰-S-组氨酰）发生氢氰化反应，分别得到相应的R和S氰醇。

Enantioselective cyanohydrin synthesis catalyzed by cyclic dipeptide by the addition of hydrogen cyanide to aldehydes is carried out. When benzaldehyde was employed as a substrate, optically active mandelonitrile, the corresponding cyanohydrin, was obtained with the enantiomeric excess (ee) of 97%and 97% chemical yield by using the cyclic dipeptide, cyclo- (Phenylalanyl-S-hisidyl) composed of two amino acid residues, Sphenylalanine and S-histidine. The stereochemical outcome of the mandelonitrile was found to be R. On the other hand, the inversion of the stereochemical preference was observed when cyclo- (S-leucyl-S-histidyl) is used as a catalyst to give S-cyanohydrins. Thus, the methodology for the cyanohydrin syntheses of both enantiomers by selecting the amino acid residue in the cyclic dipeptide is established. In addition, hydrocyanation of alpha, beta-unsaturated aldehyde by using cyclo- (S-phenyalanyl-S-histidyl) and cyclo- (S-leucyl-S-histidyl) is carried out to give the corresponding R and S cyanohydrins respectively.