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Studies with Altrose Derivatives – A Convenient Approach to α‐Linked Digitoxosides
Author(s) -
Miethchen Ralf,
Rentsch Daniel
Publication year - 1996
Publication title -
liebigs annalen
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.825
H-Index - 155
eISSN - 1099-0690
pISSN - 0947-3440
DOI - 10.1002/jlac.199619960413
Subject(s) - chemistry , deoxygenation , intramolecular force , moiety , nucleophile , acetal , stereochemistry , derivative (finance) , glycosylation , medicinal chemistry , intermolecular force , organic chemistry , catalysis , molecule , biochemistry , financial economics , economics
The 2‐ O ‐(cyclohexylcarbamoyl)‐3,4‐ O ‐(2,2,2‐trichloroethylidene)‐protected α‐altropyranosyl fluorides 1 , 7 , and 11 were used as starting materials for intra‐ and intermolecular glycosylations in the presence of BF 3 . Because of the effective neighbouring group participation of the carbamoyl moieties, the corresponding trans ‐glycosides 2 , 4 , 6 , 12 , and 14 can be stereoselectively prepared from 1 and 11 , respectively, in good yields. In the case of the 6‐ O ‐formyl derivative 7 the intramolecular glycosylation to 1,6‐anhydro‐2‐ O ‐(cyclohexylcarbamoyl)‐3,4‐ O ‐(2,2,2‐trichloroethylidene)‐β‐ D ‐altropyranoside ( 8 ) is possible, when no other competing nucleophiles are present. Furthermore, the deoxygenation of the altrose moiety of 6‐ O ‐[6‐deoxy‐3,4‐ O ‐(2,2,2‐trichloroethylidene)‐α‐ l ‐altropyranosyl]‐1,2: 3,4‐di‐ O ‐isopropylidene‐α‐ D ‐galactopyranose ( 15 ) in 2‐position and the hydrogenolysis of the trichloroethylidene acetal protecting group were simultaneously realised. 6‐ O ‐(2,6‐Dideoxy‐3,4‐ O ‐ethylidene‐α‐ l ‐ ribo ‐hexopyranosyl)‐1,2:3,4‐di‐ O ‐isopropylidene‐α‐ D ‐galactopyranose ( 16 ) was obtained by reduction of the intermediately prepared 2‐xanthate of 15 with Bu 3 SnH/AIBN.