Galactopyranose derivatives

Similarly, various a-D-glucopyranose derivatives having a mesyloxy group at C-4 and an acetoxyl group at C-l are also converted into 1,4-anhydro-/3-D-galactopyranose derivatives on treatment with sodium azide in such aprotic solvents as N,N-dimethylformamide.51 The use of sodium azide in N,N-dimethylformam ide under forcing conditions originated in attempts at nucleophilic displacements to form azido,... 

In contrast to that of glucose, the hydroxyl group at position 3 of D-galactopyranose derivatives is more reactive than that at position 2. Thus, tosylation160 of methyl 4,6-0-benzylidene-a(or -/8)-D-galactoside gives a preponderance of the 3-O-tosyl derivative admixed161-163 with a little of the 2-O-tosyl and 2,3-di-O-tosyl derivatives. 

T. Ziegler and G. Herold, Preparation of diastereomeric 3,4-O-pyruvate acetal-containing D-galactopyranose derivatives, structural assignment and use for oligosaccharide synthesis, Liebigs Ann. Chem., (1994) 859-866. 

Marra, A, Gauffeny, F, Sinay, P, A novel class of glycosyl donors anomeric S-xanthates of 2-azido-2-deoxy-D-galactopyranose derivatives. Tetrahedron, 47, 5149-5160, 1991. 

Mubarak, A, Fraser-Reid, B, Synthetic routes to 3-C-cyano-3-deoxy-D-galactopyranose derivatives,... 

A. M. Heras-Lopez, M. S. Pino-Gonzalez, F. Sarabia-Garcia, and F. J. Lopez-Herrera, Reaction of O-benzyl- and 4,6-benzylidene-D-gluco- and D-galactopyranose derivatives with amide-stabilized sulfur ylides, J. Org. Chem., 63 (1998) 9630-9634. 

Only 2-pyridyl reverse C-nucleosides are known. Coupling saccharide free radicals 831 and 834 with protonated pyridine derivatives gave the 2-pyridyl reverse C-nucleosides 832 and 835, respectively. Free radical 831 was obtained by decarboxylative photolysis of the uronic acid derivative 830 in the presence of hypervalent iodine compounds (92TL7575 (Scheme 232), whereas free radical 834 was obtained by thermal homolysis of the carbon-iodine bond in the 6-iodo-6-deoxy-o-galactopyranose derivative 833 in the presence of benzoyl peroxide (93JOC959) (Scheme 233). 

The galactopyranose derivative 248 required for coupling with the chlorin macrocycle was synthesized by following the reaction sequences described in Scheme 49 and using compoimds 251-253 [48]. 

Reductive cleavage (LiAlH -AlCl, NaCNBH -HCl, or AlCl -Me N) of 2-substituted l 6-anhydro-3 -0-endo-(M-methoxybenzylidene)-B-D-galactopyranose derivatives gave predominantly the axial 3-0 -(4-methoxybenzyl) ethers with a free -hydroxy group. -Methoxy... 

Reductive cleavage with lithium aluminium hydride-aluminium chloride, or with sodium cycloborohydride-hydrochloric acid, or with aluminium chloride-trimethylamine, of endo-3t4-0-(4-methoxybenzylidene) acetal rings of 1,6-anhydro- -D-galactopyranose derivatives gives predominantly the axial 3-0-(4-0-methoxybenzyl)ether derivatives. Oxidative cleavage with DDQ affords the axial 3-0-(4-inethoxybenzoyl)... 

The 2,4-di-C-methyl-D-galactopyranose derivative (16) has been rearranged to the furanose isomer (17) and hence to the derivative (18)(Scheme 4) required for the synthesis of an erythronolide ring fragment. 

Inch, T. D., and H. G. Fletcher, Jr. Synthesis with partially benzylated sugars. VI. Some solvolytic reactions of 2-acetamido-l-0-acyl-2-deoxy-D-glucopyranose and D-galactopyranose derivatives. J. Org. Chem. 31, 1810 (1965). 

The hypothesis of Praefcke et al. [345], that geminally branched amphiphiles form, by association, disk-like units, has been proved also for the case of galactopyranose derivatives [348, 349]. 

Specifically C-6 deuterated D-galactopyranose derivatives have been shown by n.m.r. to have the 2. preferred rotamer state about... 

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