Residue, glycosidic

In 1986 the novel chitinase inhibitor (—)-allosamidin was discovered in fermentation broths of Streptomyces sp. 1713 by Sakuda and coworkers.1 (—)-Allosamidin is unusual inasmuch as it contains two N-acetyl-D-allosamine residues glycosidically linked P-1,4 to one another. In turn, this disaccharide is connected to a cyclopentanoid known as (—)-allosamizoline in the manner shown in Figure 11.1. 

A 2-(trimethylsilyl)ethyl glycoside is convertible into a glycosyl chloride by treatment with 1,1-dichloromethyl methyl ether in the presence of zinc(II) chloride, tin(IV) chloride, or iron(III) chloride. Normally an a-chloro sugar is the product. If a (3-chloro product is formed first (kinetic product) by participation from a 2-O-substituent, this is rapidly equilibrated into the thermodynamically more stable a product (anomeric effect, Section VI). The transformation is compatible with acetyl, benzoyl, and benzyl protecting groups and most importandy, also with the presence of inter-residue glycosidic bonds 229,230... 

Table 2. Structure of some complex, non-sialo sphingoglycolipids (note that all have a lactosyl loGal-(pi 4)d-GIc1 residue glycosidically-linked to Cl of the ceramide)...

The peeled tuber is steeped and then roasted after grating, and it has been suggested that silthough this must remove most of the free cyanide, heating also inactivates the hydrolase and may thus stabilize residual glycoside which may then be ingested and metabolized in vivo with the liberation of cyanide (Stanton, R.—personal communication). 

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