- Reaction of derivatives of methyl 2,3-O-benzylidene-6-deoxy-alpha-L-mannopyranoside with butyllithium: synthesis of methyl 2,6-dideoxy-4-O-methyl-alpha-L-erythro-hexopyranosid-3-ulose.
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Methyl 2,3-O-benzylidene-6-deoxy-alpha-L-mannopyranoside (2) reacted with butyllithium to give a mixture of 1,5-anhydro-3-C-butyl-1,2,6-trideoxy-L-ribo-hex-1-enitol (3) and its L-arabino analogue (4), together with methyl 2,3,6-trideoxy-alpha-L-erythro-hex-2-enopyranoside (5). In contrast, the 4-O-methyl-analogue (8) of 2 was converted by butyllithium into methyl 2,6-dideoxy-4-O-methyl-alpha-L-erythro-hexo-pyranosid-3-ulose (9), which was further characterized as its oxime 10. The 4-O-benzyl analogue of 8, obtained as two separate diastereoisomers (6 and 7) differing in configuration at C-2 of the dioxolane ring gave a complex misture of products on treatment with butyllithium.
- Clode,Horton,Weckerle
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p. 305 - 314,307, 309, 312
(1976)
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- LEWIS-ACID-CATALYSED ISOMERISATION OF BENZYLIDENE ACETALS OF METHYL α-L-RHAMNOPYRANOSIDE AND METHYL β-L-ARABINOPYRANOSIDE DERIVATIVES
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The Lewis-acid-catalysed isomerisation of several derivatives of methyl 2,3-O-benzylidene-α-L-rhamnopyranoside and methyl 3,4-O-benzylidene-β-L-arabinopyranoside has been investigated.The presence of equatorial substituents vicinal to the benzylidene ring decreases the rate of isomerisation, and exo isomers isomerise more quickly than the corresponding endo isomers.The occurence of isomerisation during the reductive cleavage reaction of acetal rings with LiAlH4-AlCl3 has been demonstrated.
- Harangi, Janos,Liptak, Andras,Olah, V. Anna,Nanasi, Pal
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p. 165 - 172
(2007/10/02)
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