Methyl-p-D-galactopyranoside

In order to try to overcome some of the problems associated with chemical synthesis of oligosaccharides containing N-acetylneuraminic acid, Sabesan and Paulson [277] have used a combination of chemical and enzymatic methods using purified sialyl-transferases in the presence of CMP-iV-acetylneuraminic acid and synthetic acceptor molecules to give sialyl derivatives of oligosaccharides which were characterised by NMR. Thus, methyl P-D-galactopyranoside, methyl P-D-lactoside and iV-acetyl-... 

In like fashion, by careful stereochemical correlation of the three masked hydroxy stereocentres in 4 [i.e. C(13), C(14) and C(15) using FK506 numbering] with various monosaccharide derivatives (Scheme 17.3), Danishefsky was able to establish an appropriate chirality match with the C(2), C(3) and C(4) stereocentres of D-galactose. Methyl p-D-galactopyranoside was therefore selected as the starting material for his synthesis of 4. 

A. Maiadufu and S. Perlin, Synthesis of analogs of methyl p-D-galactopyranoside modified at C-4, Carbohydr. Res. 32 261 (1974). 

J. S. Brimacombe andO. A. Ching, Nucleophilic displacement reactions in carbohydrates. Part IX. The solvolysis of methyl 6-0-Methanesulphonyl-2,3-di-O-methyl-p-D-galactopyranoside A methoxy group participation. Carbohydr. Res. 9 287 (1969). 

Proton-proton coupling constants in a-D-xylopyranosyl-4-methyl-pyridinium ion and methyl-P-D-galactopyranoside. Note the differences between coupling constants associated with very similar dihedral angles and the lower couplings experienced when the proton-attached carbon atoms have multiple electron-withdrawing groups. 

Methyl P-D-galactopyranoside, treated with deuterated water in the presence of Raney nickel as catalyst and ultrasonic radiation, gives rapid C-deuteration at... 

Takagi. S. Jeffrey, G.A. Neutron diffraction refinement of the crystal structures of methyl a-D-galactopyranoside monohydrate and methyl p-D-galactopyranoside. Acta Crystallogr. Sect. B 1979. 35, 902-906. 

Separation selectivity can also be altered by the type of ion that is formed for the compound of interest. Cation or anion adducts can have a significant effect on the separation. In the positive ion mode, most ions formed from electrospray or any chemical ionization methods are protonated cations. However, if Na+ is added to the electrospray solution, sodiated adducts may be formed as the primary response ion. For example, the protonated ions of two isomers, methyl-P-glucopyranoside and methyl-a-glucopyranoside, cannot be baseline separated in DTIMS, but the sodiated adducts of the same isomers can be baseline separated. Figure 8.9 demonstrates separation selectivity induced by cation adduction. These IMS spectra are of the methyl-p-D-galactopyranoside and the methyl-a-D-galactopyranoside isomers adducted with cobalt acetate, silver, and lead acetate. The cobalt acetate adducts had a separation factor of 1.02, the silver adducts had a separation factor of 1.05, and the lead acetate adducts had a separation factor of 1.07. 

FIGURE 8.9 Selectivity induced by cation adduction. Ion mobility separation of methyl-p-D-galactopyranoside from its isomer methyl-a-D-galactopyranoside using different cation adducts. (From Dwivedi et al., Rapid resolution of carbohydrate isomers by electrospray ionization ambient pressure ion mobility spectrometry-time-of-flight mass spectrometry (ESI-APIMS-TOFMS), J. Am. Soc. Mass Spectrom. 2007, 18, 1163-1175. With permission.)... 

Methyl p-D-galactopyranoside, activated with dibutyltin oxide and treated with tetra-O-pivaloyl-a-D-glucopyranosyl bromide, gave the 6-p-linked product in 72% yield. In this work the term open glycosylation is used to imply an unprotected acceptor strategy. Related work with the glucuronic acid analogue as donor is reported in Section 1.4.8. 

The enzymatic glycosylation is carried out with both donors, p-nitrophenyl a-L-fucopyranoside 3 and a-L-fucopyranosyl fluoride 4, transferred onto the acceptor methyl p-D-galactopyranoside 5 (70) (Scheme... 

Me glycoside, 3,4-O-isopropylidene Methyl 3,4-0-isopropylidene-2,6-di-0-methyl-p-D-galactopyranoside Ci2H220 262.302... 

Mp 210°. [a]o +33 (c, 1.03 in CHCI3). Me glycoside, 4,6-O-benzylidene, 2-mesyl Methyl 4,6-0-benzylidene-2-0-mesyl-3-O-methyl-p-D-galactopyranoside [51385-25-2]... 

Methyl 4,6-0-benzylidene-2-0-methyl-a-D-altropyranoside, M-156 Methyl 4,6-O-benzylidene-3-0-methyl-a-D-altropyranoside, M-156 Methyl 4,6- 0 -benzylidene-2- O -methyl-a-D-galactopyranoside, M-249 Methyl 4,6- 0 -benzylidene-2- O -methyl- p-D-galactopyranoside, M-249 Methyl 4,6- O -benzylidene-3- O -methyl-a-D-galactopyranoside, M-250... 

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