Conformational analysis of methyl 5-O-methyl septanosides: effect of glycosylation on conformer populations.
Methyl 5-O-methyl-alpha-d-glycero-d-idoseptanoside (3) and methyl 5-O-methyl-beta-d-glycero-d-guloseptanoside (4) were investigated as (1-->5)-linked di-/oligoseptanoside mimetics. Here we report the synthesis of 3 and 4 and describe their preferred solution conformations through a combination of ab initio/DFT calculations and (1)H (3)J(H,H) NMR coupling constant analysis. The conformations of 3 and 4 observed in this study are discussed in comparison to those of the parent (C5 hydroxy) compounds 1 and 2. The results indicate that methyl 5-O-methyl-alpha-septanoside 3 is relatively rigid and adopts the same (3,4)TC(5,6) conformation as 1. Methyl 5-O-methyl-beta-septanoside 4 is somewhat less rigid than its parent septanoside (2). In addition to the (6,O)TC(4,5) conformation adopted by 2, beta-septanoside 4 also populates the adjacent (3,4)TC(5,6) conformation. Glycosylation at C5 on beta-septanoside 4 therefore increases its overall flexibility and allows access to alternative ring conformations.
DeMatteo
Matthew P
MP
Department of Chemistry, The Ohio State University, 100 West 18th Avenue, Columbus, OH 43210, USA.
Mei
Song
S
Fenton
Ryan
R
Morton
Martha
M
Baldisseri
Donna M
DM
Hadad
Christopher M
CM
Peczuh
Mark W
MW
D002236:Carbohydrate Conformation; D003198:Computer Simulation; D006031:Glycosylation; D008759:Methylglycosides / Q000138:chemical synthesis / Q000737:chemistry*; D009010:Monte Carlo Method; D019906:Nuclear Magnetic Resonance, Biomolecular
D008759:Methylglycosides