Catalyst-Directed Diastereoselectivity in Hydrogenative Couplings of Acetylene to α-Chiral Aldehydes: Formal Synthesis of All Eight l-Hexoses

Hydrogenative coupling of acetylene to α-chiral aldehydes 1a−4a using enantiomeric rhodium catalysts ligated by (S)-MeO-BIPHEP and (R)-MeO-BIPHEP delivers the diastereomeric products of carbonyl-(Z)-butadienylation 1b−4b and 1c−4c, respectively, with good to excellent levels of catalyst directed diastereofacial selectivity. Diastereomeric l-glyceraldehyde acetonide adducts 1b and 1c were converted to the four isomeric enoates 6b, 8b, 6c, and 8c, representing a formal synthesis of all eight l-hexoses.