Pyranose derivatives galacto

A comparison of the three binary copolymerizations of 1,6-anhydro-/S-D-gluco-, -galacto-, and -manno-pyranose derivatives gives some insight into the mechanism of copolymerization, if it is assumed on this evidence that the per-p-xylyl and perbenzyl derivatives can be used interchangeably.107... 

Special attention was given to the conformations about the C-5-C-6 bond in semiempirical quantum mechanical nuclear shielding calculations on a series of hexopyranoses," and in molecular mechanics simulations of methyl a- and P-d-gluco-, -galacto-, and talo-pyranoside in aqueous solution," " as well as to the conformation of the acetamido group in 2-acetamido-2-deoxy-D-allo- and -d-gluco-pyranose derivatives, such as 18-20." ... 

A six-step synthesis of 2-acetamido-l,3,6-tri-0-acetyI-4-S-acetyl-2-deoxy-4-thio-D-mannopyranose (22) from 2-acetamido-2-deoxy-D-nuumopyranose used the l,6 3,4-dianhydrosugar 21 as key-intermediate. The 4-O-triflyl-D-galacto-pyranose derivative 23 was the starting compound for the preparation of methyl 4-5-(3-hydroxy-2-pyridyl)-4-thio-P-D-glucopyranosides 24 as potential glucosi-dase inhibitors. A conformational study on L-thiohexofuranoses is referred to in Chapter 21. 

Alkyl (or acyl) derivatives of the 6-amino-6-deoxy carbohydrates are examples of derivatives in which the hydrophilic and hydrophobic moieties are linked at other positions than C-1. Thus 6-amino-6-deoxy-D-galactose derivatives 34 were prepared from l,2 3,4-di-0-isopropylidene-6-0-tosyl-a-D-galacto-pyranose by the following reactions (1) substitution of the leaving group at C-6 by a phthaloyl function, (2) hydrazinolysis to afford a 6-amino-6-deoxy intermediate, (3) reaction of acyl or sulfonyl chlorides at the amino function, (4) deprotection of the acetal rings to afford the expected glycolipid 34 [56]. 

Acetalation of l,6-anhydro-/l-D-mannopyranose (39) and -/1-D-galacto-pyranose with trichloroacetaldehyde in the presence of A,A -dicyclohexylcar-bodiimide affords endo-H diastereomers of 3,4- and 2,3-trichloroethylidene derivatives of l,6-anhydro-/l-D-altro- and -/1-D-gulopyranose, respectively.528 For isomerization of various 1,6-anhydrohexopyranoses acetates, see Section II.4. 

N. Lupescu, J. Solo-Kwan, D. Christiaen, H. Morvan, and S. (Malis) Arad, Structural determination by means of gas chromatography—Mass spectrometry of 3-0-(a-D-glucopyranosyluronic acid)-galacto-pyranose, an aldobiuronic acid derived from Porphyridium sp. polysaccharide, Carbohydr. Polym., 19 (1992) 131-134. 

Anhydrofuranoses derived from all eight diastereoisomeric aldohexoses were described in the literature [6]. These compounds are formed as side products in the synthesis of 1,6-anhy-dropyranoses from free (or partially protected) sugars. Treatment of free sugars with toluene-p-sulfonic acid in DMF solution affords the furanose and pyranose 1,6-anhydrides with the furanose form up to 33% for the galacto-, alio-, and talo- isomers [3] the example is shown in O Scheme 9. 

Two novel phosphoramidite derivatives of 2 -deoxynucleosides incorporating a pyranose-modified nucleic base have been synthesised and incorporated into short DNA sequences. The galactose-modified deoxyuridine phosphoramidite (52) was synthesised via a Heck reaction between 3, 5 -0,0-bis(tcrt-butyl-dimethylsilyl)-5-iodo-2 -deoxyuridine and 2,3,4,6-tetraacetyl-l-(6-hex-1-ynyl) galacto-pyranoside. Subsequent deprotection, 5 -0-tritylation and treatment with 2-0-cyanoethyl-iV,N-diisopropyl chlorophosphine in the presence of DIPEA offered (52) which was used for solid-phase synthesis of a new type of oligo DNA-galactose conjugate." ... 

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