Glycoside sequencing

Fig. 2. Glycoside chains and the Kunitz domains. Amino acid and glycoside sequences for the two Kunitz-binding domains of Bik are shown. C-C across a chain indicates a cross-link. Predicted fragmentation points for Bik due to trypsin exposure are shown by lines with black dots. The aprotinin-matching peptides of each Kunitz domain are shown by a darkened circle. The first peptide of aprotinin is indicated as Aprol. The X-ray structure-predicted touch points between Bik and trypsin are marked. The predicted PI peptide of the active inhibitory site sequence is indicated as well.

The aglycone segments 14 and 15 were next individually partnered with glycone 16 for the four step C-glycosidation sequence (Scheme 4). DCC mediated esterification (36) of 16 with 14 and 15 followed by treatment of the resulting esters with the Tebbe reagent (37) gave enol ethers 23 and 25 respectively, in 61 and 65% yields from 16. The key cyclization reactions on 23... 

Sfrucfurally O glycosides are mixed acefals fhaf involve fhe anomeric posifion of furanose and pyranose forms of carbohydrates Recall fhe sequence of mfermediafes m acefal formalion (Secfion 17 8)... 

The widespread occurrence and biological significance of polyoxygenated carbocycles provided the impetus to apply RCM to sugar-derived dienes. Carbohydrate carbocyclization based on a sequence of Vasella reductive opening of iodo-substituted methyl glycosides [25], and RCM of the dienes available from the resulting unsaturated aldehydes, were used to prepare a series of natural compounds (Schemes 5-7). 

Figure 35-1. A segment of one strand of a DNA molecule in which the purine and pyrimidine bases guanine (G), cytosine (C), thymine (T), and adenine (A) are held together by a phosphodiester backbone between 2 -de-oxyribosyl moieties attached to the nucleobases by an W-glycosidic bond. Note that the backbone has a polarity (ie,a direction). Convention dictates that a single-stranded DNA sequence is written in the 5 to 3 direction (ie, pGpCpTpA, where G, C,T, and A represent the four bases and p represents the interconnecting phosphates).

NMR spectroscopy To identify specific sugars, their sequence, linkages, and the anomeric nature of glycosidic linkages. 

Fig. 2.13 Generalized reaction sequence from starting amino acid [65] to product cyanogenic glycoside [66]...

The Shen group has devised a domino process wherein after an enzymatic cleavage of a glycoside a rearrangement sequence takes place [18]. Subjecting multifloroside 8-38 to P-glucosidase in acetate buffer (Scheme 8.10) afforded jasmolac-tone analogues such as 8-39 in a rather low yield. 

---