Isolation, structure elucidation, and biological evaluation of 15-amido-3-demethoxy-2alpha,3alpha-methylenedioxyerythroculine, a new alkaloid from Hyperbaena valida.

A phytochemical investigation of the leaves of Hyperbaena valida resulted in the isolation and characterization of two erythrina-type alkaloids, 1 and 2, which were found to be antagonists at nicotinic receptors. Compound 1 was assigned as the new 15-amido-3-demethoxy-2alpha,3alpha-methylenedioxyerythroculine and compound 2 as the known 3-demethoxy-2alpha,3alpha-methylenedioxyerythroculine. Antagonism of a 100 microM nicotine response was observed for alkaloid 1 (IC50 value of 94 +/- 8 microM) and alkaloid 2 (IC50 value of 77 +/- 19 microM).

Improved methods for 1H-3H heteronuclear shift correlation.

A better understanding of the structure of complex 3H-labeled molecules can be obtained by complete assignment of their 1H and 3H solution-state NMR spectra. The assignment process is aided by the detection of heteronuclear chemical shift correlations between 1H and 3H nuclei. Heteronuclear correlation (HETCOR) experiments previously applied to this task exhibit several drawbacks caused by the nature of both the pulse sequences and 1H-3H spin systems. The range of J-couplings involved in 1H-3H coupling networks make it challenging to perform correlation experiments using methods that rely on coherences created during free precession periods and interrupted by transfer pulses. Two alternative HETCOR experiments are demonstrated for 1H-3H systems in the present work and are shown to have advantages over earlier methods. The first experiment is known as hetero-TOCSY and correlates heteronuclear chemical shifts using J-cross polarization. This experiment achieves both homonuclear and heteronuclear mixing and connects the chemical shifts of all 1H and 3H nuclei in a coupling network. A second HETCOR experiment uses the heteronuclear Overhauser effect to obtain through-space correlations between nearby nuclei. The 1H-3H HETCOR experiments are phase sensitive and typically contain more correlations than other methods, which is beneficial for assignment purposes, while being sensitive enough to be applicable to routine analytical samples. The experiments were used to analyze 3H incorporation in sub-milligram quantities of 3H-labeled pharmaceutical derivatives with complex labeling schemes.

Lakshminine, a new rare oxoisoaporphine alkaloid from Sciadotenia toxifera, and structural revisions of telazoline and teladiazoline, two related oxoaporphines from Telitoxicum peruvianum and T. glaziovii.

Lakshminine (1), a novel oxoisoaporphine alkaloid possessing a C-6 amine substituent, was isolated from a basic fraction from the woody vines (collected from two bush-ropes) of Sciadotenia toxifera. This compound represents the first documented occurrence of an oxoisoaporphine from any Menispermaceae species other than Menispermum dauricum. The structures of two related aporphine alkaloids, telazoline (3) and teladiazoline (5), were revised on the basis of a comparison of their spectral data with that of lakshminine (1).

Antimicrobial resveratrol tetramers from the stem bark of Vatica oblongifoliassp. oblongifolia.

Two new resveratrol tetramers, hopeaphenol A (1) and isohopeaphenol A (2), along with the known vaticaphenol A (3), were isolated from the stem bark of Vatica oblongifolia ssp. oblongifolia through bioassay-guided fractionation. The structures and their relative stereochemistry were determined by spectroscopic techniques. Compounds 1 and 3 demonstrated moderate activity against methicillin-resistant Staphylococcus aureus and Mycobacterium smegmatis.

Rearrangement of epoxynitriles: a convenient homologation of acyclic and cyclic ketones to carboxylic acids.

A convenient two-step homologation of both aliphatic and aromatic ketones to the corresponding carboxylic acid has been developed. First ketones were converted to epoxynitriles with the Darzens reaction. Second, a Lewis acid mediated rearrangement of these epoxynitriles with lithium bromide was achieved to give homologated secondary alkanoic acids (as well as aryl-alkanoic) in good yields. The mechanism and the scope of the rearrangement reaction were investigated. This strategy constitutes a two-step homologation of ketones to secondary carboxylic acids.

A new dimeric dihydrochalcone and a new prenylated flavone from the bud covers of Artocarpus altilis: potent inhibitors of cathepsin K.

A MeOH/CH(2)Cl(2) extract of the bud covers of Artocarpus altilis collected in Micronesia showed activity in a cathepsin K inhibition assay. In addition to the three known flavonoids isolated from the bud covers of this species, two new compounds have been identified whose structures were determined on the basis of spectral data. These compounds include a dimeric dihydrochalcone, cycloaltilisin 6 (2), and a new prenylated flavone, cycloaltilisin 7 (3). Novel compounds 2 and 3 have IC(50) values of 98 and 840 nM, respectively, in cathepsin inhibition.

Haploscleridamine, a novel tryptamine-derived alkaloid from a sponge of the order haplosclerida: an inhibitor of cathepsin K.

As part of a search for novel inhibitors of cathepsin K, the MeOH extract of a Micronesian sponge of the order Haplosclerida was shown to be active. Bioassay-guided fractionation of the extract yielded halitoxins, tryptamine, and a novel tryptamine-derived alkaloid, haploscleridamine (1). The tetrahydro-beta-carboline structure of haploscleridamine (1) was elucidated through spectral techniques. Haploscleridamine (1) was found to be an inhibitor of cathepsin K with an IC(50) of 26 microM.