Structures of New Alkaloids from Rain Forest Trees Galbulimima belgraveana and Galbulimima baccata in Papua New Guinea, Indonesia, and Northern Australia

Following on our 60-year research on the chemical constituents of the rain forest trees Galbulimima belgraveana and Galbulimima baccata, we report the isolation of seven new alkaloids: GB14 (14), GB22 (15), GB25 (16), GB21 (17), GB23 (18), GB24 (19), and GB26 (20). Their structures were elucidated by a combination of spectroscopic analyses and single-crystal X-ray crystallography, as well as structure degradation and interconversion. The newly isolated alkaloids are precursors or derivatives of the known family members from our early studies and could be intermediates in the biosynthesis of the Galbulimima alkaloids. Therefore, the present study has expanded the range of structures in this family of alkaloids and provided some missing links in the biosynthetic sequences.This study was supported by the Fundamental Research Funds for the Central Universities, Chin

ISOLATION AND STRUCTURE DETERMINATION OF BISDEMTHYLAAPTAMINE FROM BUNAKEN MARINE PARK SPONGE <i>Aaptos, sp.</i>

Bisdemethylaaptamine, an alkaloid naphtyridine with molecular weight 200 and formulae molecule C11H8N2O2 has been isolated from Bunaken Marine Park sponge Aaptos sp. Isolation was done by using several stages of column chromatography and high performance liquid chromatography. Molecular weight of this naphtyridine alkaloid was determined by electron ionization (EI) and electrospray ionization (ESI) mass spectroscopies and its structure assigned to be 8,9-dihydroxy-1H-benzo[d,e][1,6]naphtyridine by proton and carbon nuclear magnetic resonances (1H and 13C-NMR).   Keywords: Sponge, Aaptos sp., naphtyridine alkaloid, bisdemethylaaptami

Improving a Natural Enzyme Activity through Incorporation of Unnatural Amino Acids

The bacterial phosphotriesterases catalyze hydrolysis of the pesticide paraoxon with very fast turnover rates and are thought to be near to their evolutionary limit for this activity. To test whether the naturally evolved turnover rate could be improved through the incorporation of unnatural amino acids and to probe the role of peripheral active site residues in nonchemical steps of the catalytic cycle (substrate binding and product release), we replaced the naturally occurring tyrosine amino acid at position 309 with unnatural L-(7-hydroxycoumarin-4-yl)ethylglycine (Hco) and L-(7-methylcoumarin-4-yl)ethylglycine amino acids, as well as leucine, phenylalanine, and tryptophan. Kinetic analysis suggests that the 7-hydroxyl group of Hco, particularly in its deprotonated state, contributes to an increase in the rate-limiting product release step of substrate turnover as a result of its electrostatic repulsion of the negatively charged 4-nitrophenolate product of paraoxon hydrolysis. The 8-11-fold improvement of this already highly efficient catalyst through a single rationally designed mutation using an unnatural amino acid stands in contrast to the difficulty in improving this native activity through screening hundreds of thousands of mutants with natural amino acids. These results demonstrate that designer amino acids provide easy access to new and valuable sequence and functional space for the engineering and evolution of existing enzyme functions

The structures of three new Galbulimima alkaloids

The structures of three new alkaloids isolated from the bark of the rain forest tree Galbulimima belgraveana, have been determined by a combination of NMR spectroscopy and X-ray crystallography. One of the alkaloids, himgrine (5), was shown to be an oxygenated derivative of himbacine (1), while the second, GB16, (8) proved to be identical with a degradation product from himgaline (4). The remaining alkaloid, GB17 (12) possesses an entirely new and unexpected skeleton

4-Alkoxycarbonyl- and aminocarbonyl-substituted isoxazoles as masked acrylates and acrylamides in the asymmetric synthesis of Δ 2 -isoxazolines

4-Alkoxycarbonyl and aminocarbonyl-substituted isoxazoles undergo conjugate reduction to give Δ2-isoxazolines on treatment with sodium borohydride and sodium trifluoroacetoxyborohydride, respectively. They are also alkylated at C5 through sonication wit

Quantification of Sideroxylonals in Eucalyptus Foliage by High-performance Liquid Chromatography

This paper describes the extraction and quantification of sideroxylonals, a group of formylated phloroglucinol compounds found in the foliage of some eucalypt species. Samples of dry, ground foliage were Soxhlet-extracted with light petroleum spirit:acetone (4:1) and the resultant extract analysed (in the presence of internal standard) by reversed-phase HPLC without further purification. The yield of sideroxylonals was exponential with time and showed an inflection at ca. 4 h of extraction. It is recommended that samples be extracted for 6 h, giving a 92% recovery of the sideroxylonals. The title compounds deteriorate under various conditions, e.g. 10% are lost when foliage is oven-dried at 40°C compared to freeze-drying. Storing sample's in mobile phase led to a slow deterioration of sideroxylonals with a 7% loss after 4 days, while 22% of these compounds were lost from dry, ground eucalypt leaf stored at room temperature for 20 months

Two Major Saponins from Seeds of Barringtonia asiatica : Putative Antifeedants toward Epilachna sp. Larvae

Two major saponins have been isolated from a methanol extract of the seeds of Barringtonia asiatica, and their structures elucidated (mainly by two-dimensional NMR spectroscopy) as 3-O-{[β-D-galacto-pyranosyl(1→3)-β-D-glucopyranosyl (1→2)]-β-D-glu

Complete assignment of the 1 H and 13 C NMR spectra of the camelliagenin A and A 1 -barrigenol from the seed of Barringtonia asiatica.

The1H and13C NMR spectra of camelliagenin A and A1-barrigenol from the seeds of Barringtonia asiatica were completely assigned for the first time by one-and two-dimensional homo-and heteronuclear studies (1H,13C, DQCOSY, TOCSY, HMQC, HMBC) at 600 and 150.89 MHz. The article reports standard data that may be important for potential authors needing such information

DNA binding of the anti-cancer platinum complex trans -[{Pt(NH 3 ) 2 Cl} 2 μ-dpzm] 2+

The DNA binding of the dinuclear platinum complex trans-[{Pt(NH 3)2Cl}2μ-dpzm]2+ (di-Pt), linked with the 4,4′-dipyrazolylmethane (dpzm) linker, was examined by 1H and 195Pt NMR and transcription assays. At 60 °C, di-Pt reacts with guanosine two-fol