32. Strukturelle Abwandlungen an partiell silylierten Kohlenhydraten mittels Triphenylphosphin/Azodicarbonsaure-diathylester

Article abstract of DOI:10.1002/hlca.19800630203

Reaction of methyl 2,6-bis-O-(t-butyldimethylsilyl)-β-D-glucopyranoside (1a) with triphenylphosphine (TPP)/diethyl azodicarboxylate (DEAD) and Ph3P.HBr or methyl iodide yields methyl 3-bromo-2,6-bis-O-(t-butyldimethylsilyl)-3-deoxy-β-D-allopyranoside (3a) and the corresponding 3-deoxy-3-iodo-alloside 3c (Scheme 1).By a similar way methyl 2,6-bis-O-(t-butyldimethylsilyl)-α-D-glucopiranoside (2a) can be converted to the 4-bromo-4-deoxy-galactoside 4a and the 4-deoxy-4-iodo-galactoside 4b.In the absence of an external nucleophile the sugar derivatives 1a and 2a react with TPP/DEAD to form the 3,4-anhydro-α- or -β-D-galactosides 5 and 6a, respectively, while methyl 4,6-bis-O-(t-butyldimethylsilyl)-β-D-glucopyranoside (1b) yields methyl 2,3-anhydro-4,6-bis-O-(t-butyldimethylsilyl)-β-D-allopyranoside (7a, s.Scheme 2).Even the monosilylated sugar methyl 6-O-(t-butyldimethylsilyl)-α-D-gluco yranoside can be transformed to methyl 2,3-anhydro-6-O-(t-butyldimethylsilyl)-α-D-allopyranoside (8; 56percent) and 3,4-anhydro-α-D-galactopyranoside 6 (10percent), whereas methyl 6-O-(tbutyldimethylsilyl)-β-D-glucopyranoside (1c) yields the 2,3-anhydro-β-D-alloside 7 (46percent) and the 3,4-anhydro-β-D-alloside 9 (23percent, s.Scheme 3).Reaction of 1c with TPP/DEAD/HN3 leads to methyl 3-azido-6-O-(t-butyldimethylsilyl)-3-deoxy-β-D-allopyranoside (10).The epoxides 7 and 8 were converted with NaNH3/NH4Cl to the 2-azido-2-deoxy-altrosides 11 and 13, respectively, and the 3-azido-3-deoxy-glucosides 12 and 14, respectively (Scheme 4 and 5).Reaction of 7 and 8 with TPP/DEAD/HN3 or p-nitrobenzoic acid afforded methyl 2,3-anhydro-4-azido-6-O-(t-butyldimethylsilyl)-4-deoxy-α- and -β-D-gulopyranoside (15 and 17), respectively, or methyl 2,3-anhydro-6-O-(t-butyldimethylsilyl)-4-O-(p-nitrobenzoyl)-α- and -β-D-gulopyranoside (16 and 18), respectively, without any opening of the oxirane ring (s.Scheme 6). - The 2-acetamido-2-deoxy-glucosides 19a and 20a react with TPP/DEAD alone to form the corresponding methyl 2-acetamido-3,4-anhydro-6-O-(t-butyldimethylsilyl)-2-deoxy-galactopyranosides (21 and 22) in a yield of 80 and 85percent, respectively (Scheme 7).With TPP/DEAD/HN3 20a is transformed to methyl 2-acetamido-3-azido-6-O-(t-butyldimethylsilyl)-2,3-didesoxy-β-D-allopyranoside (25, Scheme 8).By this way methyl 2-acetamido-4-azido-3,6-bis-O-(t-butyldimethylsilyl)-2,4-dideoxy-α-D-galactopyranoside (23; 16percent) and the isomerized product methyl 2-acetamido-4,6-bis-O-(t-butyldimethylsilyl)-2-deoxy-α-D-glucopyranoside (19d; 45percent).Under the same conditions the disilylated methyl 2-acetamido-2-deoxy-glucoside 20b leads to methyl 2-acetamido-4-azido-3,6-bis-O-(t-butyldimethylsilyl)-2,4-dideoxy-β-D-galactopyranoside (24). - All structures were assigned by 1H-NMR. analysis of the corresponding acetates.