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New Stereospecific Rearrangements of Pyranosides

 

作者: Ralf Miethchen,   Daniel Rentsch,   Michael Frank,  

 

期刊: Journal of Carbohydrate Chemistry  (Taylor Available online 1996)
卷期: Volume 15, issue 1  

页码: 15-31

 

ISSN:0732-8303

 

年代: 1996

 

DOI:10.1080/07328309608005421

 

出版商: Taylor & Francis Group

 

数据来源: Taylor

 

摘要:

Methyl β-D-arabinopyranoside (1), phenyl 1-thio-β-D-galactopyranoside (3), methyl β-L-fucopyranoside (7), methyl β-L-fucopyranoside (9), 1,6-anhydro-β-D-galactopyranoside (D-galactosan;11), and 1,6-anhydro-β-D-mannopyranoside (D-mannosan;14) were stereospecifically converted in moderate up to good yields into methyl 4-O-cyclohexylcarbamoyl-2,3-O-(2,2,2-trichloroethylidene)-β-D-lyxopyranoside (2), phenyl 4-(9-cyclohexyIcarbamoyl-6-O-formyl-2,3-O-(2,2,2-trichloroethylidene)-1-thio-β-D-gulopyranoside (4) / phenyl 4-O-cyclohexylcarbamoyl-2,3-O-(2,2,2-trichloroethylidene)-1-thio-β-D-gulopyraoside (5), methyl 4-O-cyclohexylcarbamoyl-2,3-O-(2,2,2-trichloroethylidene)-6-deoxy-α-L-gulopyranoside (8), methyl 2,3-O-(2,2,2-trichloroethylidene)-4-O-cyclohexylcarbamoyl-6-deoxy-β-L-gulopyranoside (10), 1,6-anhydro-4-O-cyclohexyl-carbamoyl-2,3-O-(2,2,2-trichloroethylidene)-β-D-gulopyranoside (12), and 1,6-anhydro-2-O-cyclohexylcarbamoyl-3,4-O-(2,2,2-trichloroethylidene)-β-D-altropyranoside (15), respectively, using a nonclassic pathway of chloral acetalisation with dicyclohexylcarbodiimide (DCC) as coagent. In the case of1,3, and9, chloral acetalisations yielded diastereomeric mixtures, e.g., the acetals2,4,5, and10consist ofendo-H/enxo-H dioxolane type acetals with preference of theendo-H form. In contrast to this, the compounds7,11, and14gave exclusively theendo-H diastereomers8,12, and15. Additionally, the structure of the anhydro compound15was confirmed by intramolecular glycosylation of the 2-O-cyclohexylcarbamoyl-3,4-O-(2,2,2-trichloroethylidene)-α-D-altropyranosyl fluoride (17). Finally, the 6-O-formyl-α-D-gulopyranoside4was alternatively deformylated by methanol/triethylamine giving5and methanol/sodium methoxide yielding phenyl 6-O-cyclohexylcarbamoyl-2,3-O-(2,2,2-trichloroethylidene)-1-thio-β-D-gulopyranoside (6). The carbamoyl protecting group of12was cleaved by refluxing with methanolic sodium methoxide solution giving 1,6-anhydro-2,3-O-(2,2,2-trichloroethylidene)-β-D-gulopyranoside (13).

 

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