beta-Alkoxy-gamma-amino Aldehydes by Internal Redox Ring Cleavages of Carbohydrate-Derived Enantiopure 1,2-Oxazines and Preparation of Heterocycles with Aminopolyol Side Chain

• Published in: Synthesis (Stuttgart) no. 1; pp. 109 - 118
• Main Authors: Al-Harrasi, Ahmed, Bouche, Lea, Zimmer, Reinhold, Reissig, Hans-Ulrich
• Format: Journal Article
• Language: English
• Published: STUTTGART Thieme Medical Publishers 01.01.2011
• Subjects: Chemistry; Chemistry, Organic; Physical Sciences; Science & Technology; carbohydrates; 1,2-oxazines; LITHIATED METHOXYALLENE; NITRONES; BUILDING-BLOCKS; PENTOSE GLYCALS; VINYL ETHERS; ACID PROMOTED REARRANGEMENT; aldehydes; 1,3-DIPOLAR CYCLOADDITION; alkylation; pyrazoles; LEWIS-ACIDS; DERIVATIVES; TRANSFORMATIONS; imidazo[1,2-a]pyrimidines
• ISSN: 0039-7881; 1437-210X
• DOI: 10.1055/s-0030-1258326

N-Methylation of syn- or anti-configured 3,6-dihydro-2H-1,2-oxazines and subsequent treatment with triethylamine smoothly provided enantiopure alpha,beta-unsaturated beta-alkoxy-gamma-amino aldehydes bearing different protected diol, triol, or tetrol side chains in good to excellent yields. The N-O bond cleavage occurs under mild conditions and involves an internal redox process. The method is also applicable to tetrahydro-2H-1,2-oxazines, which either lead to 4-amino ketose or aldose derivatives (D-sorbose or D-idose configuration). The equivalency of the generated beta-alkoxyenal moiety with 1,3-dicarbonyl compounds could be demonstrated by condensation reactions with hydrazine or 2-aminoimidazole derivatives providing a series of new pyrazole or imidazo[1,2-a]pyrimidine derivatives with stereodefined and protected aminopolyol side chains.