C-gentiobiose

FIGURE 58.1 Chemical structures of crocetin (A), crocetin diglucose ester (B), crocetin gentiobiose glucose ester (C), and crocin (D). 

Curiously, among those C/O-disaccharide pairs that have been studied by X-ray, the gentiobiose, isomaltose, and sucrose pairs each show completely different conformational behavior in the solid state. C-Lactose bound to peanut agglutinin11 has been studied, and this case will be treated later. 

Comparison Between the Experimental J Values (Hz) Described tor the Glycosidic Torsion of a Series of /3-Gentiobiose (6) and a-Isomaltose (43), (1 — 6)-Llnked C-Glycosyl Compounds, and the Expected J Values (Hz) Given in Thble I... 

Additional work in 1987 centered around studies of the preferred conformations of various C-disaccharides. Preliminary work by Kishi, era/.,13 was subsequently confirmed by the same group in 1991.14 In these reports, utilizing C-glycosidic analogs of isomaltose and gentiobiose (Figure 8.5.1), it was determined that conformations of C-disaccharides can be predicted on the basis of steric interactions alone. This conclusion, based, in part, on similarities regarding the conformations and behaviors of conventional disaccharides in variable temperature proton NMR studies, was later extended to the conformations of C-trisaccharides introduced in Chapter 1. 

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