The hexenitol (III) mentioned in the title is alkylated with the organometallic compounds (IV) to form the 1‐substituted glucals (V), (VI), and/or the 3‐substituted regioisomers (VII).
4,6-O-Benzylidene-1,2-dideoxy-d-threo-hex-1-enopyranose-3-urose reacted with allylic organometallic reagents, CH2=CR–CH2–Metal [R = H or CH3; Metal = MgCl, AlEt2, or Ti(OPri)3], to selectively give 4,6-O-benzylidene-1,2-dideoxy-3-C-(2-propenyl- or 2-methyl-2-propenyl)-d-lyxo-hex-1-enopyranose. On the other hand, the erythro isomer gave 3-C-(2-propenyl- or 2-methyl-2-propenyl)-d-arabino-hex-1-enopyranose and the corresponding ribo isomer in a ratio ranging from 1 : 1 to 10 : 1
Reaction of Hex-1-enopyranose-3-uroses with Organometallic Reagents.Regio-and Stereoselective Introduction of Allylic Substituents on Pyranose Ring.-The benzylidene hexenopyranoses (I) and (V) are treated with the allylmetal compounds (II) to form either the stereoisomeric products ( III) and (IV) or only the isomers (VI). The product ratio in the first reaction is influenced by the nature of the metal and by the substitution pattern of the allylic moiety. -(TAKIYA, M.; ISHII, M.; SHIBATA, K.; MIKAMI, Y.; MITSUNOBU, O.; Chem. Lett. (1991) 11, 1917-1920 Dep. Chem., Coll. Sci. Eng., Aoyama Gakuin Univ., Chitosedai, Tokyo 157, Japan; EN)
1,5-Anhydro-4,6-O-benzylidene-2-deoxy-3-O-mesyl-D-ribo-hex-1-enitol reacted with alkylmagnesium bromides (RMgBr: R = C2H5–, (CH3)2CH–, or C2H5(CH3)CH–) to give the corresponding 1-β-C-glycopyranosides and 3-C-alkyl-D-arabino-hex-1-enitols, while the reaction with methylmagnesium bromide afforded 1-α-C- and 1-β-C-methyl-glycosides in a ratio of 1 : 1.5–2. On the other hand, when the reaction was carried out in the presence of Cul or CuBr–S(CH3)2, substitution took place at the C-3 position to afford the corresponding 3-C-methyl-D-arabino-hex-1-enitol.
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