Wilfred R. Chan

The structure and stereochemistry of neoandrographolide, a diterpene glucoside from Andrographis paniculata nees

Abstract Neoandrographolide (2) is shown to be the β-glucoside of ent -19-hydroxy-8(17), 13-labdadien-16,15-olide. A correlation with andrographolide has been done.

GEODIAMOLIDES H AND I, FURTHER CYCLODEPSIPEPTIDES FROM THE MARINE SPONGE GEODIA SP.

Abstract Two new cyclodepsipeptides, geodiamolide H (3) and I (4), were isolated from the marine sponge Geodia sp. The structures of 3 and 4 were determined by 2D NMR spectroscopy while the absolute stereochemistry of 4 was established by X-ray crystallography. Geodiamolide H 3 was cytotoxic to some human cancer cell lines.

Extractives of Cedrela odorata L.—III: The structure of photogedunin

Abstract An extract of Cedrela odorata L. has given a non-furanoid tetranortriterpene. This is shown to be closely related to gedunin with the furan ring modified as a γ-hydroxy α,β-butenolide.

New germacrane derivatives from gorgonian octocorals of the genus Pseudopterogorgia

Abstract Two new and five known germacrane derivatives were isolated from Pseudopterogorgia americana and a related species. Their structures were established by spectroscopic methods.

Complete 13C and 1H Spectral Assignments of Prenylated Flavonoids and a Hydroxy Fatty Acid from the Leaves of Caribbean Artocarpus communis

Three prenylated flavonoids and a hydroxy fatty acid were isolated from the leaves of the seedless variety of Artocarpus communis, but only one from the leaves of the seeded variety. Two of these compounds are known to show great promise as pharmaceutical and agricultural chemicals. The 1H and 13C NMR spectra were completely assigned by using a combination of 2D NMR experiments which included 1H–1H COSY, HETCOR and FLOCK sequences.

Tobagolide, a new pseudopterane diterpenoid of the octocoral pseudopterogorgia acerosa

2-D NMR spectroscopy has established the structure of tobagolide, isolated from P. acerosa, as the novel dimethylamino derivative 1. Acetylation of 1 follows an unusual course in which NMe2 is replaced by OAc.

The structure of cleomeolide, an unusual bicyclic diterpene from cleome viscosa L. (capparaceae)

Abstract A bicyclic diterpene cleomeolide (1) C20H30O3 has been isolated from Cleome viscosa L. (Capparaceae), and its stereostructure established by chemical, spectral and X-ray crystallographic means. Crystals of 1 belong to space group P21 with a = 10.329(2)A, b = 12.468(3)A, c= 7.356(2)A,β = 109.98°, and Z = 2. The structure was solved by a multiple solution procedure and refined by full matrix least-squares to give R = 0.041 and wR = 0.051. Oxidation of 1 gave the ketone 4, which on treatment with methanolic KOH led to a facile transannular reaction to give the lactone 6

The structure and stereochemistry of spathelin, a new seco-ring a tetranortriterpene from Spathelia sorbifolia

Abstract Spathelin is shown to have structure 2 by physical and chemical methods, including a correlation with isoobacunoic acid.

Enantio-eudesmane sesquiterpenes from it Verbesina rupestris

Abstract The leaves and stems of Verbesina rupestris contain enantio-eudesmane sesquiterpenes, isolated as esters of cinnamic acid. This finding supports th

The structure of corylifuran, A clerodane-type diterpene from Croton corylifolius lam

The structure and stereochemistry of corylifuran, a clerodane-type diterpene from Croton corylifolius Lam, have been determined as 2 by chemical and spectroscopic data and X-ray crystallographic analysis.