Lee-Juian Lin

Wrightiadione from Wrightia tomentosa

Abstract A novel isoflavone wrightiadione, was isolated from Wrightia tomentosa . Determination of the carbon framework was based on the interpretation of NMR and mass spectral data, and the structure was confirmed by X-ray analysis. This compound displays cytotoxic activity against the murine P388 lymphocytic leukemia cell line (ED 50 , 1.1 μg M1 −1 ).

Alkaloid distribution in some species of the papilionaceous tribes sophoreae, dalbergieae, loteae, brongniartieae and bossiaeeae☆

Abstract Quinolizidine and dipiperidine alkaloid profiles have been determined for various plant parts of ten papilionaceous species in the tribes Sophoreae, Da

NMR assignments of huperzine a, serratinine and lucidioline

Abstract The spectral properties of huperzine A, serratinine and lucidioline, three Lycopodium alkaloids isolated from Huperzia serrata were assigned un

6-deoxyclitoriacetal from Clitoria macrophylla

Abstract A new rotenoid, 6-deoxyclitoriacetal, was isolated from the roots of Clitoria macrophylla and its structural assignment was established unambiguously by a series of HETCOR, COLOC and NOE difference experiments. In vitro tests showed that this compound possessed strong cytotoxic activity against cultured P-388 lymphocytic leukemia cells, but was not active with cultured KB cells. However, marginal activity was observed with vinblastine-resistant KB-V1 cells, and this was enhanced by the addition of vinblastine. This rotenoid may, therefore, interact with P-glycoprotein.

3-O-Demethylswertipunicoside from Swertia punicea

Abstract A novel bisxanthone C-glycoside, 3- O -demethylswertipunicoside, structurally related to swertipunicoside, was isolated from whole plants of Swertia punicea . Determination of its structure was based on the interpretation of the spectroscopic data, particularly selective INEPT NMR spectra, and characterized as 1,3,5,8-tetrahydroxy-7-(1′,3′,6′,7′-tetrahydroxy-9′-oxo-4′-xanthyl) xanthone 2′-C-β- d -glucopyranoside.

8-methoxyingol esters from the latex of Euphorbia hermentiana

Abstract Two new ingol esters, 3,12- O -diacetyl-7- O -benzoyl-8-methoxyingol and 3,12- O -diacetyl-7- O -tigloyl-8-methoxyingol, were isolated from an acetone-soluble fraction of the latex of Euphorbia hermentiana . These macrocyclic diterpenes were identified on the basis of their spectroscopic parameters, as well as those of their hydrolytic derivatives. A third methoxylated ingol ester and a fourth new compound were tentatively identified as 3,12- O -diacetyl-7- O -angeloyl-8-methoxyingol and 3,7,12- O -triacetyl-8- O -benzoyl-18-hydroxyingol, respectively. All four new compounds, and three further ingol ester constituents of known structure, were found to be easily separable using a newly developed isolation procedure involving droplet counter-current chromatography.

Application of the SINEPT pulse programme in the structure elucidation of coumarinoligans

The SINEPT pulse programme has provided an unambiguous method for determining the structures of natural products with the 1,4-dioxane ring system such as daphneticin (3), propacin (5), and aquillochin (6).

Valerian-Derived Sedative Agents. I. On the Structure and Spectral Assignment of the Constituents of Valmane Using the Selective INEPT Nuclear Magnetic Resonance Technique

The valepotriates, a group of chemically unstable iridoid triesters possessing sedative activity, contain various ester groups at the C-l, C-7, and C-11 positions. Using the selective INEPT NMR technique and employing a suitable polarization delay for long-range coupling, it was possible to achieve the assignment and location of the ester groups directly, without ambiguity, and without chemical modification. Six valepotriates isolated from Valmane tablets served as examples to demonstrate the utility of this NMR technique. During the course of this work, the “acevaltrate” fraction was shown to be a mixture of 1-α-ace valtrate (3) and 7-β-acevaltrate (4), the structures of valtrate (1) and didrovaltrate (2) were confirmed directly, and two new valepotriates, 5a and 5b, were obtained as an inseparable mixture and characterized.

Synthesis of coumarinolignans through chemical and enzymic Oxidation

The first syntheses of coumarinolignans through chemical or enzymic oxidation of a dihydroxycoumarin and a phenylpropene are described.

Reaction of α-Haloketones with ortho-Dihydroxy-2H-1-benzopyran-2-ones. Formation of α-Pyrano-1,5-benzodioxapines-A New Heterocyclic System

Abstract Reaction of 7,8-dihydroxy-2H-1-benzopyran-2-one, and its 4-methyl derivative, with α-haloketones affords α-pyrano-1,5-benzodioxapines, while 3-chloro-4-methyl-7,8-dihydroxy-2H-1-benzopyran-2-one gives α-pyrano-1,4-benzodioxane. The structures of the compounds were deduced using a combination of 1H nmr, 13C nmr (BB, DEPT), HETCOR, NOESY, and selective INEPT techniques and molecular modeling.