Lyxopyranoside methyl 2,3-anhydro

The 4-triflates 277, 279, and 281 of benzyl 2,3-anhydro-o -D- and -) -L-ri-bopyranosides and -a-D-lyxopyranoside gave, - readily, on reaction with BU4NF [CgHg (24 h) or MeCN (5-8 h), r.t.], the respective 2,3-anhydro-4-deoxy-4-fluoro derivatives 278,280, and 282 in good yields. The conformation ( //s) of the starting compounds remained the same after fluorination. Methyl 2,3-anhydro-4-deoxy-4-fluoro-a-L-lyxopyranoside (284, 86%) was prepared from the 4-triflate 283 by treatment with EtjN- 3HF (CH2CI2-EtjN, 40°, 5 h). 

Honeyman147 reported the synthesis of methyl 2,3-anhydro-/3-L-lyxopyranoside, and claimed that, on alkaline hydrolysis, this gives a 2 1 ratio of L-xyloside L-arabinoside, but these results could not be substantiated by Buchanan and R. Fletcher,68 who recorded different constants for the epoxide and for the disulfonic ester claimed147 to be the starting material for its synthesis. The same epoxide has been synthesized by Reist and coworkers,160 and its properties are in agreement with Buchanan and Fletcher s results. Ethyl or methyl 3,4-anhydro-/3-L-ribopyranoside undergoes substitution at C-4 in all the reactions thus far studied. Neither half-chair conformation would seem to be clearly favored, but the specificity observed can be rationalized by considering the steric and polar interactions that may arise in the transition state substitution at C-3 in conformation 58 would involve marked interactions between the nucleophile and... 

Condensation between the acetylated glycosyl bromide derived from the (3-1,4-linked xylobiose and methyl 2,3-anhydro- 3-L-lyxopyranoside afforded a route to the glycoside of the )3-l, 4-xylose-linked trimer, amd the isomeric (1- 3),(l- 4)-]3-linked trisaccharide was obtained by standard glycosylation of a methyl 4-0-j3-D-xylopyranosyl-D-xyloside derivative having a free hydroxyl group at C-3... 

Me glycoside, 2,3-anhydro Methyl 2, 3-anhydro-4-bromo-4-deoxy-a-L-lyxopyranoside [106966-39-6]... 

Methyl 2,3-anhydro-4-bromo-4-deoxy-a-L-lyxopyranoside, B-84 Methyl 2,3-anhydro-4-bromo-4-deoxy-6- O -trityl-a-D-gulopyranoside, B-78 Methyl 2,3-anhydro-4-chloro-4-deoxy-a-L-xylopyranoside, C-110 Methyl 2,3-anhydro-6-deoxy-a-D-allopyranoside, A-516 Methyl 2,3-anhydro-6-deoxy-a-L-allopyranoside, A-516 Methyl 3,6-anhydro-2-deoxy-4,5 7,8-di-0-isopropylidene-D-g-/ycer(3-D-ia/o-octonate, M-174... 

Neighboring group effect. Methyl 2-0-acetyl-3,4-anhydro-a-D-arabinopyrano-side heated 0.5 hr. at 100° with 80%-acetic acid, and the intermediate mixture of 2 monoacetates deacetylated overnight with Na-methoxide in methanol -> methyl a-D-lyxopyranoside. Y 63%. - Due to the presence of a frans-acetoxy group, opening of the oxide ring occurs unidirectionally. F. e. s. J. G. Buchanan and R. Fletcher, Soc. 1966 (G), 1926. 

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