Hydrogen bonding of fluorinated saccharides in solution: F acting as H-bond acceptor in a bifurcated H-bond of 4-fluorinated levoglucosans
Hydrogen bonding of fluorinated saccharides in solution: F acting as H-bond acceptor in a bifurcated H-bond of 4-fluorinated levoglucosans
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DOI：
10.1002/hlca.200790196
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发表时间：
2007-01-01
影响因子：
1.8
通讯作者：
Vasella, Andrea
中科院分区：
文献类型：
--
作者：
Bernet, Bruno;Vasella, Andrea
4-合成氟化的左旋葡聚糖以测试即使当O中心点F距离增加时OH中心点中心点F H键是否可行。氟化1，6-脱水-β-D-吡喃葡萄糖由1，6：3.4-二脱水-β-D-吡喃半乳糖合成（8）。用KHF 2和KF处理8得到43%的4-脱氧-4-氟聚葡萄糖（9），其通过甲硅烷基化转化为3-O-保护的衍生物13，通过甲硅烷基化、乙酰化和脱甲硅烷基化转化为15。制备了4-脱氧-4-甲基左旋葡聚糖（19）和4-脱氧左旋葡聚糖（21）作为参比化合物，它们只能从HO-C（2）到O-C（5）形成二价氢键。它们由8的（Pr 3Si）-Pr 1-保护的衍生物合成。4-氟代左旋葡聚糖在CDCl_3溶液中的分子内分叉氢键由HO-C（2）到F-C（4）和O-C（5）由H-1-NMR标量偶联（h_1）J（F，OH）和（3）J（H，OH）证明。OH中心点F H键在O中心点F距离为约3.0因此，在非极性溶剂中，至少当通过同时形成OH中心点中心点O H键而有利时，形成埃。
4-Fluorinated levoglucosans were synthesised to test if OH center dot center dot center dot F H-bonds are feasible even when the O center dot center dot center dot F distance is increased. The fluorinated 1,6-anhydro-beta-D-glucopyranoses were synthesised from 1,6:3.4-dianhydro-beta-D-galactopyranose (8). Treatment of 8 with KHF2 and KF gave 43% of 4-deoxy-4-fluorolevoglucosan (9), which was transformed into the 3-O-protected derivatives 13 by silylation and 15 by silylation, acetylation, and desilylation. 4-Deoxy-4-methyllevoglucosan (19) and 4-deoxylevoglucosan (21) were prepared as reference compounds that can only form a bivalent H-bond from HO-C(2) to O-C(5). They were synthesised from the (Pr3Si)-Pr-i-protected derivative of 8. Intramolecular bifurcated H-bonds from HO-C(2) to F-C(4) and O-C(5) of the 4-fluorinated levoglucosans in CDCl3 solution are evidenced by the H-1-NMR scalar couplings (h1)J(F,OH) and (3)J(H,OH). The OH center dot center dot center dot F H-bond over an O center dot center dot center dot F distance of ca. 3.0 angstrom is thus formed in apolar solvents, at least when favoured by the simultaneous formation of an OH center dot center dot center dot O H-bond.