Synthesis of Enantiopure Functionalized (beta)-Alkoxy (gamma)-Amino Aldehydes by a New Internal Redox Ring Cleavage of Carbohydrate-Derived 1,2Oxazines

N-Methylation of 3,6-dihydro-2H-1,2-oxazines such as syn-1 or anti-1 followed by treatment with triethylamine smoothly furnished enantiopure (beta)alkoxy (gamma)-amino aldehydes syn-2 and anti-2 in excellent yields. This mild NO bond cleavage may be classified as internal redox process. Similar transformations of related 1,2-oxazines led to the expected compound anti6 or to protected 4-amino hexose derivative 10. Starting from syn-2 or anti2 condensation with hydrazine afforded new pyrazole derivatives syn-11 and anti-11 with stereodefined and protected amino diol side chain. Heterocycles syn-12 and syn-13 were prepared from syn-2 by condensation with 2-aminoimidazole or 2-aminobenzimidazole, respectively.