Reversal of optical induction in transamination by regioisomeric bifunctionalized cyclodextrins1This paper is dedicated to the memory of Derek Barton, an extraordinary chemist and role model.1

摘要: Abstract Two isomeric compounds have been synthesized carrying a pyridoxamine on C-6 of β-cyclodextrin and an imidazole unit the neighboring glucose residue. Each one stereoselectively transaminates phenylpyruvic acid to produce phenylalanine, with opposite stereochemical preferences. Structure determinations by X-ray crystallography NMR spectroscopy indicate that units serve block proton addition from their side, rather than acting protonate transamination intermediates. Related cyclodextrin–pyridoxamine had reported ethylenediamine instead imidazoles, high enantioselectivities in were claimed. Our work indicates these claims are incorrect, only poor selectivities seen often unrelated position units. Neither transaminating systems yet approaches enantioselectivity chirally mounted internal base group.