72869-13-7Relevant academic research and scientific papers
Reaction of O-benzyl- and 4,6-O-benzylidene-D-gluco- and D- galactopyranose derivatives with amide-stabilized sulfur ylides: Stereoselectivity and reactivity
Heras-Lopez,Pino-Gonzalez,Sarabia-Garcia,Lopez-Herrera
, p. 9630 - 9634 (2007/10/03)
The reaction of N,N-diethyl-2-(dimethylsulfuranylidene)acetamide (1) with protected monosaccharides has been extended to several O-benzyl- and 4,6-O-Benzylidene-D-gluco- and -D-galactopyranose derivatives. When the monosaccharide is 2,3,4,6-tetra-O-benzyl-D-glucose (6) or D-galactose (9), elimination of the 3-benzyloxy substituent occurs, to give the unsaturated epoxyamides 7 and 10, respectively, in reasonable yields and poor stereoselectivity. On the other hand, the reaction of 1 with the 4,6-O- benzylidene-D-glucopyranose derivatives 11, 14, and 17 yielded the corresponding epoxyamides 12, 15a:15b, and 18a:18b in good yields and variable stereoselectivity. In accordance with previous studies concerning the configurational assignments for the epoxide derivatives 3, 5a, and 21, obtained from 2, 4, and 20, respectively, the present article confirms the role of the hydroxyl group at C-2 on the stereoselectivity of the reaction. Thus, when the C-2 OH is unprotected (4, 11, 20), the major epoxide formed has the configuration 2S, 3R (epoxyamides 5a, 12, and 21). Conversely, derivatives with the hydroxyl group protected at C-2, or 2-deoxy sugars (2, 14, and 17), yield as the major epoxides the corresponding 2R, 3S isomers (3, 15b, and 18b).
HYDROGENOLYSIS OF THE ISOMERIC 1,2:4,6-DI-O-BENZYLIDENE-α-D-GLUCOPYRANOSE DERIVATIVES WITH THE LiAlH4-AlCl3 REAGENT
Liptak, Andras,Imre, Janos,Harangi, Janos,Nanasi, Pal
, p. 217 - 226 (2007/10/02)
Both isomers of 1,2:4,6-di-O-benzylidene-α-D-glucopyranose (and their 3-O-acetyl and 3-O-benzyl derivatives) have been prepared and their 1H- and C13-n.m.r.spectra assigned.The mode of hydrogenolysis of the dioxolane ring in these isomers by the LiAlH4-Al
Evidence for Bicyclic Oxonium Ions in the Nitrous Acid Deamination of Benzyl 2-Amino-4,6-O-benzylidene-2-deoxy-D-glucopyranosides
Chan, Wai-Pan,Gross, Paul H.
, p. 1369 - 1373 (2007/10/02)
The nitrous acid deamination of conformationally rigid benzyl amino-4,6-O-benzylidenedeoxy-D-hexopyranosides was studied: benzyl 2-amino-4,6-O-benzylidene-2-deoxy-α-D-altropyranoside (5) and benzyl 3-amino-4,6-O-benzylidene-3-deoxy-α-D-glucopyranoside (4) in aqueous dioxane both gave some benzyl 2,3-anhydro-4,6-O-benzylidene-α-D-allopyranoside (2).Thus, a trans-diaxial arrangement of hydroxyl and amino groups in the ground state does not appear to be an absolute requirement for epoxide formation, although such an arrangement clearly is most conducive to this reaction, as a comparision of yields showed.Benzyl 2-amino-4,6-O-benzylidene-2-deoxy-α-D-mannopyranoside (7) under similar conditions gave, by elimination, benzyl 4,6-O-benzylidene-α-D-erythro-hexopyrano-3-uloside (8) and, by benzyloxy migration, 2-O-benzyl-4,6-O-benzylidene-D-glucopyranose (11).Contrary to expectation, the same products, 8 and 11, were isolated from the deamination of benzyl 2-amino-4,6-O-benzylidene-2-deoxy-α-D-glucopyranoside (10) and its α-D-mannopyranoside analogue (7).A bicyclic oxonium ion is postulated as an intermediate for the deamination of the α-D-gluco isomer.Benzyl 2-amino-4,6-O-benzylidene-2-deoxy-β-D-glucopyranoside (13), with nitrous acid, gave benzyl 4,6-O-benzylidene-2-deoxy-β-D-erythro-hexopyrano-3-uloside (14).Here also, a bicyclic oxonium ion appears to be involved.All products isolated in this or earlier work from the deamination of 2-amino-4,6-O-benzylidene-D-glucopyranosides can be explained by mechanisms involving bicyclic oxonium ion intermediates.Such intermediates are apparently not involved in the deamination of the manno or altro analogues.
