Synthetic studies on d-biotin. Part 7: A practical asymmetric total synthesis of d-biotin via enantioselective reduction of meso-cyclic imide catalyzed by oxazborolidine

An Overview of Highly Optically Pure Chloramphenicol Bases: Applications and Modifications

“…Compound 9a was easily prepared from commercially available (1S,2S)-ANP and used as a chiral oxazaborolidine catalyst by Chen and co-workers [30]. This compound can catalyze an efficient enantioselective reduction of mesocyclic imide to yield (3aS,6R,6aR)-hydroxylactam with enantioselectivity of 98% as determined by chiral HPLC analysis.…”

Chloramphenicol Base: A New Privileged Chiral Scaffold in Asymmetric Catalysis

“…Despite the wide applications in asymmetric alkynylation reactions, ANP‐derived chiral amino alcohol ligands have also demonstrated high efficiency in the asymmetric reduction of carbonyl compounds. In 2003, Chen developed an efficient enantioselective reduction of meso ‐cyclic imide 14 via the use of a chiral oxazaborolidine catalyst, which was in situ generated from safe and convenient lithium hydride, boron trifluoride etherate and ANP‐derived chiral ligand 1 c . After simple addition of sat.…”

Catalytic enantioselective reductive desymmetrisation of achiral and meso compounds

“…The most efficient results within this chemistry are summarised in Scheme 1. 38 The highest enantioselectivities have been reported for the biotin intermediate 13, which was efficiently prepared in up to 98% ee and high yields using standard 39 or polymer-bound 40 oxazaborolidines derived from the amino alcohols 11 and 14 (Schemes 1(b) and (c)). Chen et al reported that achieving high degrees of enantioselectivity in the standard reduction with boron reagents required considerably high amounts of catalyst 11 (25 mol%); however, they also described a noteworthy enantioselective desymmetrisation utilising a polymer-bound catalyst 14 in lower amounts (10 mol%), which they were able to reuse in up to fourteen cycles with no loss of enantioselectivity (mean ee: 98%).…”