Galactopyranose preparation

M. Cerny, I. Cerny, and T. Trnka, Ammonolysis of l,6-anhydro-2,4-di-0-tosyl-/l-D-glucopyranose and l,6 3,4-dianhydro-2-0-tosyl-/l-D-galactopyranose preparation of 4-amino-l,6-anhydro-4-deoxy-/J-D-manno- and -/1-D-altropyranose, Carbohydr. Res., 67 (1978) 33-41. 

Starting from (—)-29, carba-a-D-galactopyranose (7) and carba-) -D-glu-copyranose (94) have been synthesized by a reaction analogous to that employed in the preparation of the racemates. - ... 

Difluoro compounds have been prepared by treatment of carbonyl compounds with DAST. These are methyl 5-deoxy-5,5-difluoro-2,3,-0-isopropylidene-)S-D-ribofuranoside, 6-deoxy-6,6-difluoro-1,2 3,4-di-0-isopropylidene-a-D-galactopyranose, methyl 2-deoxy-2,2-difluoro-... 

Deoxy-3-[ F]fluoro-D-glucose ( F-3DFG) was prepared - 454,467,473-476 essentially according to the procedure for the cold synthesis (see Section 11,2), namely, treatment of248 with Cs F (in DMF or HMPA), tetraalkylammonium [ F]fluoride (DMF, HMPA, or MeCN) or K F (in acetamide). 6-Deoxy-6-[ F]fluoro-a-D-galactopyranose was likewise pre-pared aceording to the cold synthesis. ... 

The phosphonium salt X derived from 1,2 3,A-di-0-isopropylidene-a-D-galactopyranose was readily prepared ( ), and the ylide derived from it was condensed effectively with both aliphatic and aromatic aldehydes. The products all had the a-D-galacto configuration, and the aliphatic aldehydes afforded only the Z-isomers. The less constrained permethylated phosphonium salt XI was also prepared, and... 

The first polymerizations reported by Kops and Schuerch147 were those of l,4-anhydro-2,3,6-tri-0-methyl-/3-D-galactopyranose and 1,4-anhydro-2,3-di-0-methyl-a -L-arabinopyranose. The latter compound was slightly contaminated with l,4-anhydro-2,3-di-0-methyl-a-D-xy-lopyranose, but the course of the polymerization could nevertheless be monitored reasonably accurately. For the most part, the polymerizations were conducted at 10% concentration (g/mL) in dichloro-methane, or aromatic hydrocarbons, with 1-5 mol% of phosphorus pentafluoride, or boron trifluoride etherate. At low temperature (—78 to —97°), the d.p. of both polymers produced was —90 at increasing temperatures of polymerization, termination processes became more severe, and the d.p. lower. Usually, the reaction times were long (perhaps unnecessarily so), and the conversions were 50 to 90%. The specific rotations of the D-galactans prepared at —28 and —90° differ by only —10° ( — 85 to — 95°), but those of the L-arabinans varied from + 6... 

Preparation of the Pentafluorophenylthionocarbonate 46 The disaccharide 45 [Eq. (19)] (0.1 mmol) was diluted with 1 mL of dry toluene, and (V-hydroxysuccinimide (0.1 mmol) was added. Pentafluorophenyl chlorothionoformate (0.12 mmol) was then added dropwise, and finally anhydrous pyridine (0.5 mmol) was added. The yellow reaction mixture was heated to 80°C until TLC indicated that the reaction was complete. The product was purified by placing the entire reaction mixture on a 2 x 16-cm bed of silica gel and eluting with 4 1 petroleum ether-diethyl ether to give 0-(3,4,6-tri-C>-beiizyl-2-0-[(pentafluorophenoxy)thiocarbonyl]-P-D-glucosyl)-(l— 6)-l,2 3,4-di-0-isopropylidene-a-D-galactopyranose 46 in 77% yield and as a colorless oil [a]D —53.8° (c 0.40, CHClj). 

Benzyl trifluoromethanesulfonate. Preparation of tri-O-acetyl-2-O-benzyl-a-D-galactopyranosyl bromide from 1,3,4,6-tetra-O-acetyl-a-D-galactopyranose, R. U. Lemieux and T. Kondo, Carbohydr. Res., 35 (1974) C4-C6. 

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. 

M. Cerny, O. Julakova, and J. Pacak, Preparation of 2-amino-1,6-anhydro-2-dcoxy-/i-n-glucopyranose and 2-amino-1,6 3,4-dianhydro-2-deoxy-/3-D-galactopyranose, Collect. Czech. Chem. Commun., 39 (1974) 1391-1396. 

D. J. Ward, W. A. Szarek, and J. K. N. Jones, An evaluation of methods for the preparation of l,2 3,4-di-0-isopropylidene-a-D-galacto-hexodialdo-l,5-pyranose. Oxidation of l,2 3,4-di-0-isopropylidene-a-D-galactopyranose with lead tetraacetate/ pyridine, Carbohydr. Res., 21 (1972) 305-308. 

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