Tetramate derivatives by chemoselective Dieckmann ring closure of allo -phenylserines, and their antibacterial activity.

A general route which provides direct access to substituted bicyclic tetramates, making use of Dieckmann cyclisation of oxazolidine derivatives derived from allo -phenylserines, is reported. Of interest is the high level of diastereoselectivity observed for the N -acylation reaction of oxazolidines and the complete chemoselectivity of their ring closure in the Dieckmann cyclisation. Significantly, the sense of the chemoselectivity is different to earlier reported threo -phenylserine systems, showing the importance of steric bulk around the bicyclic ring system. The derived C7-carboxamidotetramates, but not C7-acyl systems, exhibited potent antibacterial activity against MRSA, with the most active compounds exhibiting well-defined physicochemical and structure-activity properties. This work clearly demonstrates that densely functionalised tetramates are both readily available and may exhibit high levels of antibacterial activity.