6-O-a-D xylopyranosyl

Jennings and Jones95,96 prepared chlorosulfates of /3-D-glycosyl chlorides by the reaction of free sugars with sulfuryl chloride in chloroform and pyridine. 6-O-a-D-Xylopyranosyl-D-mannose (46) was prepared by the reaction of /J-D-xylopyranosyl chloride 2,3,4-tris(chlorosulfate) (44) with l,2,3,4-tetra-0-acety]-/3-D-mannopyranose (45) in the presence of silver carbonate, silver perchlorate, and Drierite, followed by removal of the protecting groups. 

Methyl 2-0-p-D-xylopyranosyl-a-L-arabinopyranoside, X-29 Methyl 2-0-p-D-xylopyranosyl-P-L-arabinopyranoside, X-29 Methyl 2-0-a-E>-xylopyranosyl-a-D-mannopyranoside, X-48 Methyl 3-O-a-D-xyIopyranosyl-a-D-mannopyranoside, X-49 Methyl 2-6>-p-D-xylopyranosyl-a-D-mannopyranoside, X-50 Methyl 3-0-p-D-xyIopyranosyl-a-i>mannopyTanoside, X-51 Methyl 2-0-a-D-xylopyranosyl-p-i>xylopyranoside, X-75 Methyl 3-0-a-D-xylopyranosyl-p-D-xyIopyrajioside, X-76 Methyl 4-0-a-D-xylopyranosyl-p-D-xylopyranoside, X-77 Methyl 2-0-p-D-xylopyranosyl-p-D-xylopyranoside, X-78 Methyl 3-0-p-D-xylopyranosyl-p-D-xylopyranoside, X-79 Methyl 4-0-p-D-xylopyranosyl-p-D-xylopyranoside, X-80 Methyl p-D-xylopyranosyl-(l ->4)-p-D-xylopyranosyl-(l 4)-p-D-xylopyranoside, X-90... 

Glycosyl fluorides have also been prepared by treatment of per-O-acyl or partially 0-acylated sugars with hydrogen fluoride [liquid HF (for example, see Refs. 38 and 39) or HF in acetic acid or dichloromethane], as exemplified by 2,3,4-tri-O-benzyl-a-D-xylopyranosyl (18), a-D-glucopyranosyl (19), tetra-O-pivaloyl-a-D-glucopyranosyl (20), and 2,3,5-tri-O-acetyl-D-xylofur-anosyl fluorides (21) (see Table 1). Frequently, HF treatment - leads to... 

C9H20O4S2 D-Ribose diethyl dithioacetal (DRETAC)316 CuH15C107 Tri-0-acetyl-/ -D-xylopyranosyl chloride (TACXYP)317 CuH1605 2,3,4-Tri-O-acetyl-a-D-xylopyranose (TAXYLP)318 C12H220,i -HoO 6-O-a-D-Galactopyranosyl-a.fl-D-glucopyranose, monohydrate (MELIBM03)319... 

Successively from the chloroform-methanol and methanol extracts also some flavonoids were obtained kaempferol 3-0-a-L-rhamnopyranoside (31), quercetin 3-0-a-L-rhamnopyranoside (8), myricetin 3-O-a-L-rhamnopyranoside (32), myricetin 3-0-(2"-0-(3-D-xylopyranosyl)-a-L-... 

To a solution of silver triiluoromethanesulfonate (7.71 g, 30 mmol) in dry dichloromethane (100 mL) at —40°C in the dark is added dropwise a solution of 9-fluorenylmethoxycarbonyl serine benzyl ester 11 (8.45 g, 20 mmol), 2,3,4-tri-O-benzoyl-a-D-xylopyranosyl bromide 12 (11.14 g, 21.2 mmol) and tetramethyl urea (3.65 g, 31.4 mmol) in dichloromethane (100 mL). After 18 h of stirring at room temperature, the precipitate is filtered off and washed with dichloromethane (200 mL). The organic solution is washed with water (200 mL), 1% KHCOj solution (twice 200 mL) and water, dried with Na SO, and concentrated in vacuo. The crude product is recrystallized from ethyl acetate-n-hexane. (If the reaction was not complete, chromatography on silica gel 60 in toluene/ethanol 9 1 is recommended). Yield 15 g (87%) mp 136°C, [ot]D -27.8° (c 1.3, CHC13), Rf 0.64 (toluene/ethanol 26 1). 

Conformational equilibria of 2,3,4-tri-O-acetyl-a-D-xylopyranosyl imidazole. The neutral compound exists as a mixture of both conformations, the protonated species exclusively in the lC4 conformation... 

Further reactions have been performed with 2,4-diethoxypyri-midine as the basic component and 2,3,4-tri-O-acetyl-L-arabino-pyranosyl bromide,7 2,3,4-tri-O-acetyl-a-D-xylopyranosyl bromide,7 2,3,4,6-tetra-O-acetyl-a-D-galactopyranosyl bromide,7 and 2,3,4-tri-O-acetyl-D-ribopyranosyl bromide8 as halogenoses the products... 

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