Hydrocyanations Inoue catalyst

The Inoue laboratory reported the first asymmetric hydrocyanation of an aldehyde using a synthetic peptide, cydo[(S)-Phe-(S)-His] (38), to give the cyanohydrin of benzaldehyde in high optical purity (up to 90% ee at 40% conversion). The ee-value of the product was found to diminish with increased reaction time (Scheme 6.5) [57]. The catalytic activity of 38 is presumed to arise from the bifunctional character of the catalyst, wherein aldehyde activation occurs through hydrogen-... 

The Strecker reaction is defined as the addition of HCN to the condensation product of a carbonyl and amine component to give a-amino nitriles. Lipton and coworkers reported the first highly effective catalytic asymmetric Strecker reaction, using synthetic peptide 43, a modification of Inoue s catalyst (38), which was determined to be inactive for the Strecker reactions of aldimines (see Scheme 6.5) [62], Catalyst 43 provided chiral a-amino nitrile products for a number of N-benzhydryl imines (42) derived from substituted aromatic (71-97% yield 64->99% ee) and aliphatic (80-81% yield <10-17% ee) aldehydes, presumably through a similar mode of activation to that for hydrocyanations of aldehydes (Table 6.14). Electron-deficient aromatic imines were not suitable substrates for this catalyst, giving products in low optical purities (<10-32% ee). The a-amino nitrile product of benzaldehyde was converted to the corresponding a-amino acid in high yield (92%) and ee (>99%) via a one-step acid hydrolysis. 

Scheme 30.1 Asymmetric hydrocyanation using Inoue s catalyst 2.

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