PHOSPHORYLATED SUGARS .27. SYNTHESIS AND REACTIONS, IN ACID-MEDIUM, OF 5-O-SUBSTITUTED METHYL 3-DEOXY-ALPHA-D-MANNO-OCT-2-ULOPYRANOSIDONIC ACID 4-PHOSPHATES

Synthesis of the alpha-methyl glycosides of 5-O-methyl-, 5-O-benzyl-8-O-methyl-, and 5,7,8-tri-O-methyl-3-deoxy-D-manno-oct-2-ulosonic acid 4-phosphates are described. The corresponding 'reducing' glycose, formed upon hydrolysis at pH 4 and 100-degrees-C, immediately eliminates the phosphate group. The olefinic acids thus produced from 5-O-methyl-, and from 5-O-benzyl-8-O-methyl 4-phosphates are not stable under these conditions: they are transformed into 4,7- and 4,8-anhydro-derivatives which have no ethylenic protons and show negligible absorption in the region 220-300 nm. The olefinic acid produced from the 5,7,8-tri-O-methyl derivative is unable to form such an anhydro-derivative: two ethylenic protons are present in its H-1 NMR spectrum and, like other conjugated olefinic alpha-keto acids, it has a strong UV absorption band (lambda-max 235 nm, epsilon 8000).