One‐pot Preparation of (S)‐N‐[(S)‐1‐Hydroxy‐4‐methyl‐1,1‐diphenylpentan‐2‐yl]pyrrolidine‐2‐carboxamide from L‐Proline

The development of economical and practical one-pot multistep synthesis is described in this article, in which the reaction product from the initial step is used directly without purification for the next step, thus affording 5 directly from proline. Moreover, the chiral amino alcohol 2, as the coupling partner, can be prepared and used directly without purification from the corresponding amino acid ester 1. For the direct coupling process of proline with 2, the Boc-protected proline is first generated in situ from proline and Boc2O (1 equiv).8 Successive treatment with ethyl chloroformate and the amino alcohol 2 yields the N-Boc proline amide 4. Subsequent removal of the Boc-group using concentrated HCl in MeOH-CH2Cl2 as a clean, reliable and convenient deprotection method is another key feature of the procedure presented herein Keywords: (S)-2-Amino-4-methyl-1,1-diphenylpentan-1-ol; (S)-N-[(S)-1-Hydroxy-4-methyl-1,1-diphenylpentan-2yl]pyrrolidine-2-carboxamide; Proline-based chiral organocatalysts