Synthesis of hydantoin analogues of (2S,3R,4S)-4-hydroxyisoleucine with insulinotropic properties

The first synthesis of an optically pure (2R,3R,4S)-hydantoin 2, analogue of (2S,3R,4S)-4-hydroxyisoleucine, was achieved in two steps in un-optimized 35% overall yield from previously reported aldehyde synthon 1. (2R,3R,4S)-Hydantoin is stable at acidic pH. This solves the major drawback of (2S,3R,4S)-4-hydroxyisoleucine that easily cyclizes into inactive lactone. Furthermore, (2R,3R,4S)-hydantoin stimulates the insulin secretion by 150% at 25 μM compared with 4-hydroxyisoleucine and insulin secretagogue drug repaglinide. In view of its stability and biological activity, (2R,3R,4S)-hydantoin represents a good candidate for type-2 diabetes management and control.