Glycosides structural features

The naturally occurring oxetanocin A (18) and synthetic oxetanocin G (19) represent a novel class of nucleosides possessing antiviral propmies. Modification of die unique oxetanosyl-lV-glycoside structural feature of 18 and 19 into the carbocyclic nucleoside framework led to the synthesis of 20 and 21 as racemates and enantiomers, which have shown activity against herpesviruses and HIV.22b,c,24,25 in view of the potent and selective anti-HCMV properties of the l -enantiomer of 21, the synthesis of the R sto eoisomer 22 was undertaken and accomplished. 

Indolocarbazole glycosides have attracted considerable interest over the years, as most indolo[2,3-fl]pyrrolo[3,4-c]carbazole alkaloids possess this structural feature. These systems are beyond the scope of this review however, there are several studies where glycosides of the parent system 1 have been investigated, in some... 

A recent phytogeny of the genus (Soltis et al., 2001) revealed that the South American taxa are most closely related to species from eastern Asia. In terms of flavonoid profiles, this requires us to reappraise the significance of the simple compounds. Thus, as suggested above, the simple flavonoid glycoside profile of C. valdivicum appears to represent a loss of biosynthetic capacities, in particular, extra oxygenation, and not a simple profile to which structural features were added in later stages of evolution. 

The structure and properties of starch have formed the subject of very extensive investigations. As a result, the main structural features and the highly polymeric nature of the molecule are now well established, and starch is known to consist of chains of D-glucopyranose units joined in the main by 4 —> 1-a-D-glycosidic linkages. 

The structural features of the solanum alkaloids are based on two primary skeletal configurations solanidane, with or without glycoside functionalities, as featured by the toxic and teratogenic steroidal alkaloids a-chaconine and a-solanine with the indolizidine type E-F ring (Figure 2.7a) and the spirosolane... 

Another structural feature that has been found only in this series of aglycones is the presence of an acetoxyl group at C-16. Glycosides with a ( -configuration for this group are shown in Fig. (12). 

Several triterpene glycosides isolated from the sea cucumbers Cucumaria echinata and Pentamera calcigera contain a carbonyl group at C-23 in the side chain, Fig. (15). This structural feature is absent in 3(i-hydroxyholost-9(l l)-ene aglycones. 

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