Methyl d-arabino-hex-2-ulopyranosonate as a building block for spiro[1,4-benzoxazine-2,2′-pyrans]

A novel glycosyl donor, methyl (3,4,5-tri-O-acetyl-β-d-arabino-hex-2-ulopyranosyl)onate bromide, obtained in two steps from methyl β-d-arabino-hex-2-ulopyranosonate, was converted into its α-nitrophenyl glycoside, which in turn was reductively cyclized to form acetylated benzoxazinoid spirans. Deprotection led to (2S)-3′,4,4′,5′-tetrahydroxy-d-arabino-2H-1,4-benzoxazin-2-spiro-2′-pyran-3(4H)-one and (2S)-3′,4′,5′-trihydroxy-d-arabino-2H-1,4-benzoxazin-2-spiro-2′-pyran-3(4H)-one. Analogous compounds are prepared from 5-methoxy-2-nitrophenol. The new class of spiro functionalized carbohydrates is structurally related to natural benzoxazinone acetal glucosides. The assignment of configuration and conformation of all products was based on 1H NMR H,H coupling constants and optical rotation values.