Modified with carbohydrate derivatives

Water extraction studies of the carbohydrate modified resins in the earlier study indicate that a portion of the carbohydrate is apparently incorporated into the final cured resin. The absolute amount of modifier incorporated into the cured resin increases with the amount initially added during resin formulation. IR studies indicated that the carbohydrate derivative is probably incorporated into the resin via ether linkages. 

Nucleophilic ring opening of epoxides with heteroatom nucleophiles is another valuable method for the synthesis of many heteroatom-modified carbohydrate derivatives. The cyclic nature of epoxides renders the competing elimination process stereoelectronically unfavorable. Analogous to the above-discussed Sn2 nucleophilic mechanism, nucleophiles can open epoxide rings, and give rise to Walden inversion at the attacked carbon, furnishing a-hydroxy derivatives as illustrated in O Scheme 10. 

The asymmetric reduction of ketones with modified lithium aluminum hydride is well known. Several reviews of the literature are available2-4-7, as is a comparison of the relative effectiveness of a variety of reagents8. Many of the early studies used terpenoid or carbohydrate-derived alcohols as modifiers, however, ketone reduction rarely proceeded with greater than 20% ee. One problem with these reagents is that the alkoxy aluminum reagent may undergo exchange so that lithium aluminum hydride could be present in solution. 

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