US EPA

1199687 

Journal Article 

ORGANOFLUORINE COMPOUNDS AND FLUORINATING AGENTS .12. FROM MANNO-PYRANOSIDES TO 3,4-O-(2,2,2-TRICHLOROETHYLIDENE)ALTROPYRANOSYL FLUORIDES IN ONLY 2 REACTION STEPS 

Miethchen, R; Rentsch, D 

1994 

1 

Synthesis
ISSN: 0039-7881
EISSN: 1437-210X 

GEORG THIEME VERLAG 

STUTTGART 

8 

827-831 

WOS:A1994PB65000022 

Methyl alpha-D-mannopyranoside (1) and methyl alpha-L-rhamnopyranoside (9) react with chloral and dicyclohexylcarbodiimide (DCC) in an one-pot reaction selectively to form the alpha-D-altropyranoside 2 and alpha-L-altropyranoside 10, respectively, in good yield. The glycosyl donor 3 was prepared from 2 by treatment with hydrogen fluoride/ nitromethane/acetic anhydride. Compound 2 can be deprotected stepwise by treatment with methanol/sodium methanolate at r. t. to 4, and heating under reflux to methyl 3,4-0-(2,2,2-trichloroethylidene)alpha-D-altropyranoside (5). Treatment of the dihydroxy derivative 5 with hydrogen fiuoride/nitromethane/acetic anhydride gave an anomeric mixture of the alpha/beta-D-altropyranosyl fluorides 6. Acylation of 5 with benzoyl or pivaloyl chloride gave the corresponding 2,6-diacyl derivatives 7 and 8, respectively. Finally, the alpha-L-altropyranoside 10 was deprotected in boiling methanol/sodium methanolate to afford the alpha-L-altropyranoside 11 and fluorinated in hydrogenfluoride/nitromethane/acetic anhydride to alpha-L-altropyranosyl fluoride 12. The various functionalized altropyranoses differ partially in their conformations. The ratio of the endo-H to exo-H diastereomers of the chloral acetals was determined. 

CARBOHYDRATES; SELECTIVE INVERSION; CHLORAL ACETALS; ALTROPYRANOSYL FLUORIDES; ANHYDROUS HF SYSTEMS