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.