Preparation of n-pentenyl glycosides

Standard Fischer glycosylation of the unprotected sugar with n-pentenol under acidic conditions works well for glucose, mannose [53] and fiicose [54] (e.g. 

13 17). The commercially available but expensive n-pentenol may be successfully recovered after this procedure by distillation and saved for subsequent applications. Koenigs-Knorr glycosylation of suitable glycosyl bromides with, for example, silver triilate (suitable for perbenzoylated glycosyl bromides [47]) or silver carbonate (for peracetylated bromides [55]) also provides access to NPGs (e.g. 

Preparation of n-pentenyl glycosides pent-4-enyl a/(S-D-glucopyranoside from D-glucose [53]. 

Round-bottomed flask (100 cm ) with water condenser and magnetic stirrer bar Magnetic hotplate stirrer with silicon oil heating bath and temperature probe Syringe (10 cm ) and needle 

Microsyringe (0.5 cm ) and needle Equipment for vacuum distillation Column chromatography equipment 

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Preparation of n-pentenyl glycosides Lewis acid mediated glycosylation of acetyl 3,6-di-0-acetyl-2,4-di-0-benzyl-a-D-mannopyranoside with 4-penten-l-ol [58]. 

A summary of (most of) the fundamental reactions of n-pentenyl glycosides is presented in Scheme 2 [2]. Being simple alkyl glycosides, NPGs can be readily prepared... 

Ability of performing multistep mechanochemical reactions is demonstrated by one-pot, four-step preparation of 3-hydroxy triazoles from acetobromo-a-o-glucose 227 (Scheme 4.57) [2]. Optimized synthetic protocol for 0-aUcylation of glycosides described earlier in this chapter was successfully used in the first reaction step, and n-pentenyl glycoside 228 was obtained by 2h milling in 83% yield. Glycoside... 

One-pot preparation of 3-hydroxy triazoles from n-pentenyl glycosides. 

Preparation of NPGs may be carried out by standard procedures for making alkyl glycosides (Scheme 3) [6]. The most direct method is the Fischer glycosidation (5 —> 1, Scheme 3), in which the aldose is treated with n-pentenyl alcohol [8] and an acid catalyst... 

Although the methodology introduced by Sinay and advanced by Chenault does essentially work, glycoside synthesis using such vinyl ethers has no definite advantage over methods such as the trichloroacetimidate or n-pentenyl approaches detailed above and suffers from relatively non-trivial procedures required in the preparation of the donor species. However, a useful application of vinyl glycosides in oligosaccharide synthesis has subsequently been developed and applied successfully by Boons. 

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