Gerhard Rücker

Alkaloids from Hypecoum leptocarpum

Two new alkaloids, named isohyperectine and leptocarpine, were isolated from the whole plants of Hypecoum leptocarpum, along with the eight known alkaloids, dihydrosanguinarine, 8-acetonyldihydrosanguinarine, 8-methoxydihydrosanguinarine, oxohydrastinine, allocryptopine, protopine, hyperectine and corydamine. All structures were determined by spectroscopic methods.

Cucurbitacins from Wilbrandia ebracteata

Abstract Three new cucurbitacins were isolated from the roots of Wilbrandia ebracteata and their structures established as 16α, 23α-epoxy-2β,3β,20β-trihydroxy-10α,23β-cucurbit-5,24-dien-11-one, 16α,23α-epoxy-2β,3β,20β-trihydroxy- 10α,23α-cucurbit-5,24-dien-11-one and 2β,3β,16α,20,25-pentahydroxy-10α-cucurbit-5,23-dien-11-one, mainly by spectroscopy.

Stereoselective Reduction of Cyclic 2, 3-Epoxyketones to Trans-2,3-Epoxyalcohols

Abstract No qeneral method for the preparation of trans-2,3-epoxyalcohols (2) by reduction of the corresponding epoxyketones (1) with borohydrides2) is described in the literature3). Reaction conditions for each epoxyketone have to be individually established to obtain a high yield of the trans-alcohol4)(2).

Flavonoids from Eschscholtzia californica

Abstract Two new isoflavones, together with quercitrin have been isolated from whole plants of Eschscholtzia californica . The structures of the new isoflavones were determined as 2′-methoxyformononetin and 7-methoxy-2′,4′-dihydroxyisoflavone by spectroscopic methods.

Triterpenoid glycosides from Stauntonia hexaphylla

On the basis of spectroscopic and chemical methods, the structures of two new bisdesmosidic triterpenoid glycosides, named staunoside D and E, which were isolated from Stauntonia hexaphylla, were established as 3-O-(beta-D-glucopyranosyl(1-->2)-[beta-D- glucopyranosyl(1-->3)]-beta-D-glucopyranosyl)-hederagenin-28- O-[beta-D-glucopyranosyl (1-->6)-beta-D-glucopyranosyl] ester and 28-O-[alpha-L-rhamnopyranosyl (1-->4)-beta-D-glucopyranosyl(1-->6)-beta-D-glucopyranosyl]ester, respectively. Three known triterpenoid glycosides were also isolated. A new proglycoside was isolated from the cleavage of the ester-glycosidic linkage and its structure characterized.

A non-oxidized melampolide and other germacranolides from Aristolochia yunnanensis

Abstract Four sesquiterpene lactones have been isolated from the underground parts of Aristolochia yunnanensis growing in the Yunnan province of China. Three were identified as the known germacranolides costunolide, dehydrocostuslactone and α-cyclocostunolide. The structure of the fourth compound, the non-oxidized melampolide, was elucidated by spectroscopic methods and X-ray analysis.

Bisepoxylignan glycosides from Stauntonia hexaphylla

Abstract Three bisepoxylignan glycosides were isolated from Stauntonia hexaphylla . One is a new compound, (+)-1-hydroxysyringaresinol-1-β- d -glucoside named staunoside C, whilst the other two, (+)-fraxiresinol-1-β- d -glucoside and (+)-1-hydroxypinoresinol-1-β- d -glucoside, are reported in this genus for the first time. Structures were established on the basis of spectroscopic analysis and chemical evidence, and their 1 H NMR signals were assigned in detail by means of 2D-NMR techniques.

Triterpenes with a new 9-epi-cucurbitan skeleton from Senecio selloi

From the fresh aerial parts of Senecio selloi (Asteraceae), two diastereomeric triterpenes with a hitherto unknown skeleton have been isolated. The structure has been elucidated mainly by advanced NMR experiments, including inverse techniques, HMQC, HMBC, ROESY.

Oxidized aristolane sesquiterpenes from Aristolochia debilis

Abstract The underground parts of Aristolochia debilis have afforded three new aristolane type sesquiterpenes: 1(1O)-aristolenal-(15), 1α-hydroperoxy-1(10)aristolenone-(2); and 9α-hydroxy-9-aristolenone-(8).

Isobicyclogermacrenal from aristolochia manshuriensis

Abstract The previously unknown (+)-isobicyclogermacrenal was isolated from Aristolochia manshuriensis. Its structure was elucidated by spectroscopic means and X-ray analysis.