Access to <i>Syn</i> α‐Amino‐β‐Hydroxyesters by N−H Insertion on <i>O</i>‐Protected α‐Diazo‐β‐Hydroxyesters

Abstract The N−H insertion reaction is a versatile method for creating C−N bonds under mild conditions, providing in particular an efficient access to both natural and non‐natural α‐amino acid derivatives. In this field, the direct N−H insertion on α‐diazo‐β‐hydroxyesters has not yet been investigated and constitutes a significant challenge, due to competitive migration processes. We report herein the first N−H insertions on O ‐protected α‐diazo‐β‐aryl‐β‐hydroxyesters, enabling to synthesize a wide range of α‐amino‐β‐hydroxyesters by tuning the nature of the amine and the aryl substituent. Overall, 28 N−H insertion products have been isolated, with moderate to good yields in most cases, and diastereoisomeric ratios up to 8.0 : 1 in favor of the syn diastereoisomer.