Hartmut Schick

Dodecaacetylprodelphinidin B3 from the dried leaves of Ziziphus spina-christi

Abstract The ethanolic extract (10% of the dried leaves) of Ziziphus spina-christi was acetylated leading to the isolation of a crystalline dodecaacetylprodelphinidin B3, which has not been described in the literature. Its structure was determined on the basis of its 1 H and 13 C NMR spectra. The main components of the extract are glucose (4.4%), sucrose (21%), dimers, oligomers and polymers of prodelphinidins (16%), betulinic acid (1.7%), sitosterol β- d -glucoside (2%), (+)-gallocatechin (1.7%) and (−)-epigallocatechin (0.9%). The structures of the crystalline peracetates were proven by comparison with the physical properties described in the literature. Proanthocyanidins and betulinic acid seem to be chemotaxonomically characteristic of Ziziphus species.

X-Ray structure analysis of procyanidin B1

Abstract Dimeric procyanidins are widespread in fruits. Their physiological effect as antioxidants is of importance. Since they possess five stereogenic centers they occur in diastereomeric forms. The biogenesis is discussed. The constitution and configuration of procyanidin B1 is proved by X-ray structure analysis of its decaacetyl derivative.

COMPOSITION OF AN ANTHOCYAN CONCENTRATE FROM ARONIA MELANOCARPA ELLIOT : X-RAY ANALYSIS OF TETRAACETYL PARASORBOSIDE

Following acetylation of an anthrocyan concentrate from black chokeberries (fruits of Aronia melanocarpa Elliot = Sorbus melanocarpa Heynh., Rosaceae), which is used as a natural food colouring agent, hexa-O-acetyl-sorbitol, penta-O-acetyl-glucopyranose (1), tetra-O-acetyl-β-D-glucopyranosyl benzoate (2), and hepta-O-acetyl-amygdalin (7) were detected by comparison with authentic samples. The structures of the hitherto unknown compounds 4-O-(tetra-O-acetyl-β-D-glucopyranosyl)pentan-2-one (3) and hepta-O-acetyl (2-pentanyl)-β-D-gentiobioside (8) were elucidated from their 1H,1H- and 13C,1H-COSY spectra. The structure of tetra-O-acetyl parasorboside was confirmed by crystal structure analysis.

Chemistry of the Ginkgolides. Part 10: Access to 14C-Labelled Ginkgolide A

Abstract In four reaction steps, ginkgolide A ( 1 ) was synthesized from the enol-acetate 3 , which is available in six steps from 1 . The key step was the reaction of the α-epoxy-acetate 4 with the lithium enolate of methyl propionate to give the compounds 5 and 6 . 14 C-Labelled ginkgolide A, which is of interest for pharmacological studies, can be synthesized using the 14 C-labelled methyl propionate.

Preparation of Kingiside from Aucubin

The tetraacetyl derivative 8 of the naturally occurring kingiside (8a) was prepared from aucubin (1). Intermediates in the synthesis were (8S)-tetraacetyl loganin (6) and (8S)-tetraacetyl-7-ketologanin (7), whose free (8R)-epimers occur in many different plants (Caprifoliaceae, Loganiaceae). The 13C NMR spectrum allows the structure to be unequivocally identified.