Diastereoselective preparation of novel tetrahydrooxazinones via heterocycloaddition of N-Boc, O-Me-acetals

Under Lewis acid conditions, reaction of N-Boc, O-Me acetals with the (R)-(+)-O-vinyl-pantolactone does not lead to the expected dihydrooxazine, but to the corresponding tetrahydrooxazinone, as a result of the loss of the t-Bu group. A diastereoselective and asymmetrical way to these new heterocyclic compounds is described, together with the first evidence of their ability to undergo N-acylation.