Über die Gerbstoffe aus dem Holz der Edelkastanie und Eiche, V. Die Struktur des Vescalins

Abstract

Der aus dem Holz der Edelkastanie (Castauea sativa) und der Eiche (Quercus sesseliflora) isolierte Gerbstoff Vescalin besitzt die Struktur 2a und ist damit anomer zu Castalin. Die Struktur wird bewiesen durch die saure Hydrolyse zu Flavogallonsaure (1 a) und D-Glucose sowie durch NMR-und Massenspektren der Verbindungen 2b-d. Durch Einwirkung von Methanol/Natriummethylat auf 2b wird das Neovescalin-Derivat 3a erhalten, dessen Struktur in entsprechender Weise aufgeklart wird. On Tanning Compounds from the Wood of Chestnut and Oak, V l ) . The Structure of VescalinThe tanning compound vescalin isolated from the wood of chestnut (Castunea sativa) and oak (Quercus sesseliflora) has structure 2a and is anomeric to castalin. This structure is proved by acid hydrolysis to flavogallonic acid (la) and D-glucose, and also by NMR-structural analysis as well as mass spectroscopic measurements of 2bd. With sodium methoxide/ methanol 2b produces the neovescalin derivative 3a, the structure of which is elucidated in the same manner.Der aus dem Holz von Castanea sativa und Quercus sesseli'ora isolierte Gerbstoff Vescalin3) (2a) hat nach Analyse und massenspektrometrischer Molekulargewichtsbestimmung seiner Derivate 2b und 2c die Summenformel C27H20018. Vescalin ist danach isomer mit Castalin4), das durch Erhitzen seiner wal3rigen Losung in Vescalin uberfiihrbar ists). Es wird somit verstandlich, dab auch Vescalin (2a), wie Castalin4), unter verscharften Hydrolyse-Bedingungen Flavogallonsaure6) (1 a) und eine geringe Menge D-Glucose liefert.

Reinvestigation of the Stereochemistry of the C-Glycosidic Ellagitannins, Vescalagin and Castalagin

“… Therefore, the calculations were performed with des-HHDP analogues of vescalagin and castalagin (i.e., vescalin and castalin, formerly proposed structures were 3 ′ and 4 ′, respectively) (Figure ). Vescalin and castalin are produced by the hydrolysis of vescalagin and castalagin, respectively, and these compounds can be found in plants belonging to the genus Quercus. , An initial conformational search of structures 3 ′, 4 ′ and structures 3 , 4 with the ( S , S ) and ( S , R ) configurations was performed using the Monte Carlo method at the MMFF94 force field, and the resulting low-energy conformers within 6 kcal/mol of each other were optimized at the AM1 level and then reoptimized at the B3LYP/6-31G(d,p) level in MeOH using the PCM model. The lowest energy conformers of 3 ′ and 3 are shown in Figure .…”

Vegetable Tannins

“…Equat ion 61 Roux and his collaborators 16 ,69,70 were able in the 1960's to characterise a group of profisetinidins (40)(41)(42) from the wood of Acacia mearnsii. Using spectroscopic and chemical techniques they fully determined their structures as indicated.…”

Fundamental Methods in Ellagitannin Synthesis

“…Isocorilagin ( 7) is an -glucosyl gallate [11]. Furthermore, there is neither the HHDP group (1) nor glucopyranose (3) in vescalin (8) [12].…”