Regioselective ring opening of benzylidene acetal protecting group(s) of hexopyranoside derivatives by DIBAL-H.
The reductive ring-opening reaction of benzylidene-protected glucosides and mannosides such as methyl 2,3-di-O-benzyl-4,6-O-benzylidene-alpha-d-glucoside (1) and methyl 2,3-di-O-benzyl-4,6-O-benzylidene-alpha-d-mannoside (4) by using a toluene stock solution of DIBAL-H and a dichloromethane stock solution of DIBAL-H gives mainly or selectively the corresponding 2,3,4-tri-O-benzyl derivatives (2, 5) and 2,3,6-tri-O-benzyl derivatives (3, 6), respectively, although that of methyl 2,3-di-O-benzyl-4,6-O-benzylidene-alpha-d-galactoside (7) gives methyl 2,3,6-tri-O-benzyl-alpha-d-galactoside (9) selectively irrespective of the solvent of the stock solution of DIBAL-H. Similarly, the reaction of the exo-isomer of methyl 2,3:4,6-di-O-benzylidene-alpha-d-mannopyranosides (exo-10) with a toluene stock solution and dichloromethane stock solutions of DIBAL-H selectively gives methyl 3-O-benzyl-4,6-O-benzylidene-alpha-d-mannoside (12) and methyl 2-O-benzyl-4,6-O-benzylidene-alpha-d-mannoside (11), respectively, although that of endo-10 selectively affords 11, irrespective of the solvent of the stock solution of DIBAL-H.
Tanaka
Nobuo
N
Department of Applied Chemistry, Okayama University of Science, Okayama 700-0005, Japan.
Ogawa
Izumi
I
Yoshigase
Shigeki
S
Nokami
Junzo
J
D000080:Acetals / Q000737:chemistry*; D002236:Carbohydrate Conformation; D002621:Chemistry / Q000379:methods; D004187:Disaccharides / Q000138:chemical synthesis*; D015195:Drug Design; D005697:Galactosides / Q000737:chemistry; D008956:Models, Chemical; D015394:Molecular Structure; D009942:Organometallic Compounds / Q000737:chemistry*; D011714:Pyrans / Q000737:chemistry*; D012997:Solvents / Q000737:chemistry; D013237:Stereoisomerism; D013997:Time Factors
D000080:Acetals; D004187:Disaccharides; D005697:Galactosides; D009942:Organometallic Compounds; D011714:Pyrans; D012997:Solvents; C035719:diisobutylaluminum