Cenek Kolar

Semisynthetic ε-(iso)rhodomycins: a new glycosylation variant and modification reactions

Abstract Synthesis of 7- O -(3-amino-2,3,6-trideoxy-α- l - lyxo -hexopyranosyl)-e-(iso)rhodomycinones 16 and 17 , and their 3′-morpholino derivatives are described. Glycosylation (trimethylsilyl triflate, 10:1 dichloromethane-acetone, −35°) of 1- O - tert -butyldimethylsilyl-2,3,6-trideoxy-4- O - p -nitrobenzoyl-3-trifluoroacetamido-β- l - lyxo -hexopyranose ( 4 ) with e-rhodomycinone (e-RMN, 5 ) or e-isorhodomycinone (e-isoRMN, 6 ) afforded 7- O -α-glycosyl-e-RMN ( 9 ) and -e-isoRMN ( 12 ) in high yield. The glycosyl donors 2,3,6-trideoxy-4- O - p -nitrobenzoyl-3-trifluoroacetamido- l - lyxo -hexopyranose ( 2 ) or its 1- O -trimethylsilylated α-anomer 3 were less suitable for the glycosylation of these aglycons. Saponification of 9 and 12 provided 16 and 17 , respectively, which reacted with various 2,2′-oxydiacetaldehydes under conditions of reductive alkylation to give 3′-morpholinyl-e-(iso)rhodomycins.