Derivatives of the 2-amino-1,2,3,4-tetrahydronaphthalene, IV. Synthesis and configuration of the diastereomeric 2,3,4a,5,10,10a-hexahydro-4H-naphth[2,3-b]-1,4-oxazines ('Naphthalanmorpholines')

Article abstract of DOI:10.1002/cber.19781110334

The reaction of the trans-hydroxy-amino acid 4 with acetic anhydride in pyridine yielded the trans-azalactone 5, which has been converted into the morpholine derivative trans-3b by LiAlH₄ reduction in presence of an excess of borontrifluoride. It has been established in this way that the 'naphthalanmorpholine' (3a) synthesized earlier by L. Knorr on the route 1 → 2a → 3a possesses the trans-configuration. The corresponding cis-isomer of 3a has been obtained by treatment of the aminodiol cis-6c with sulfuric acid and following hydrogenolysis of the N-benzyl group. Therefore, the sulfuric acid dehydration leading to the cyclic ethers 3 occurs stereospecifically.