Studies on the Selective Reduction of the Amide Link of Acyclic and Macrocyclic Amidoketals: Unexpected Cleavage and trans‐Acetalization with Red‐Al^®

Abstract

Selective reduction of the amide moiety of acyclic and macrocyclic amidoketals was studied in presence of various reagents (BH₃ · Me₂S, iBuAlH₂, Red‐Al^®, LiAlH₄). The best results were obtained with lithium aluminium hydride in the presence of triethylamine traces, whereas borane dimethyl sulfide gave rise to a partial ketal reduction of the acyclic compound and Red‐Al^® to a cleavage of the macrocyclic molecule accompanied by an unexpected trans‐acetalization.

Keywords:

• acyclic and macrocyclic amido and aminoketals
• selective reduction
• trans‐acetalization

Acknowledgment

The authors thank B. Légeret and F. Pélissier for performing the mass spectra, R. Egrot for recording the 2D NMR spectra, and Professor A. Alexakis for valuable discussions.