engleski

Crystal structures, circular dichroism spectra and absolute configurations of some L-ascorbic acid derivatives

Chiral 2, 3-O, O-dibenzyl ethers of L-ascorbic acid with 4-(5, 6-epoxy)- (4) and 6-O-tosyl- (8) functional groups were studied by X-ray crystallography and circular dichroism (CD) spectroscopy. The stereostructure of 2, 3-O, O-dibenzyl-5, 6-isopropylidene-L-ascorbic acid (6) and 8 was determined by X-ray crystal structure analysis. Comparison of the CD-spectra of 4 and 8 with the CD-spectra of their synthetic precursors (2-3, 5-7) and L-ascorbic acid (1) itself, as well as crystal structures of 6 and 8 permitted to deduce the absolute configuration of 4. Thus, the chiral atoms C-4 and C-5 in 4 have R- and S- configurations, which is consistent with the configuration of 1.

L-ascorbic acid derivatives ; single crystal X-ray diffraction ; circular dichroism spectroscopy ; Cotton effect

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