Brian L. Marquez

Scytonemin-a marine natural product inhibitor of kinases key in hyperproliferative inflammatory diseases

Chronic inflammatory diseases are associated with the persistent production of proinflammatory mediators and tissue hyperplasia. Protein kinases play an important role in regulating the signaling events controlling mediator release and cell proliferation. For instance, in in vivo models, the tumor promoter, phorbol myristate acetate (PMA), is used as an initiator of inflammation, both acute and chronic. PMA produces these effects by activating protein kinase C (PKC), an enzyme involved in a number o f cellular activities, including growth, differentiation, and mediator formation [1]. In addition, cell cycle progression is highly regulated predominantly through kinase activity. One example is polo-like kinase 1 (PLK1), an enzyme important for the G2-M transition and mitotic spindle formation. Therefore, by targeting certain kinases involved in both processes, it may be possible to reduce the adverse nature o f chronic inflammatory disorders. Here we report the novel pharmacological properties o f scy-

Biosynthetic Pathway and Origin of the Chlorinated Methyl Group in Barbamide and Dechlorobarbamide, Metabolites from the Marine Cyanobacterium Lyngbya majuscula

Abstract Structural and biosynthetic studies have been conducted on the barbamide class of molluscicidal agent. Dechlorobarbamide was isolated from a Curacao collection of the marine cyanobacterium Lyngbya majuscula and its structure determined through spectroscopic analysis and comparisons with barbamide. The absolute stereochemistry of the dolaphenine moiety of barbamide was determined to be S , defining the absolute configuration of barbamide as 2 S ,7 S . Stable isotope feeding experiments conducted with cultured L. majuscula have provided clear evidence that barbamide biosynthesis involves chlorination of the unactivated pro - R methyl group of leucine. Experiments with l -[ 2 H 10 ]leucine demonstrated that chlorination of the pro- R methyl occurs without detectable activation via the leucine-catabolic pathway. Moreover, an extremely high level of incorporation of fed [2- 13 C]-5,5,5-trichloroleucine into barbamide indicates that leucine is the probable substrate for the chlorination reaction. Incorporations of [1,2- 13 C 2 ]acetate and [1- 13 C, 1- 18 O]acetate confirmed the origins of C-5 and C-6 whereas incorporation of l -[3- 13 C]phenylalanine supported the hypothesis that the phenyl group and its three carbon side-chain in barbamide (C-7, C-8 and C-10–C-16) arise from phenylalanine. The thiazole ring (C-17–C-18) of 1 was shown to likely arise from cysteine through a [2- 13 C, 15 N]glycine feeding experiment. Detection of intact 13 C– 15 N bond was observed by application of a new GHNMBC NMR experiment. Results from this latter feeding experiment also indicated that the N–CH 3 and O–CH 3 groups of 1 originate from the C 1 pool; this was supported by enrichment in these methyl groups when cultures were provided with l -[methyl- 13 C]methionine.

Curacin d, an antimitotic agent from the marine cyanobacterium Lyngbya majuscula

Curacin D is a novel brine shrimp toxic metabolite isolated from a Virgin Islands collection of the marine cyanobacterium Lyngbya majuscula. Structure elucidation of curacin D was accomplished through multidimensional NMR, GC/MS, and comparisons with curacin A. Curacin D provides new insights into structure-activity relationships in this natural product class as well as some aspects of the likely biosynthetic pathway of the curacins.

[6-13C]-(2S,4S)-5-Chloroleucine: synthesis and incubation studies with cultures of the cyanobacterium, Lyngbya majuscula

Abstract [6-13C]-(2S,4S)-5-Chloroleucine 12 was prepared in six steps and 26% overall yield from protected l -glutamic acid using 13CH3I as the source of isotopic label. On feeding 12 to cultures of L. majuscula no incorporation of isotopic label into the trichlorinated marine natural product barbamide was detected. The synthesis of a novel dichloroleucine derivative 16 is also described.

Bruchins, Plant Mitogens from Weevils: Structural Requirements for Activity

Bruchins are 3-hydroxypropanoate esters of long-chain α,ω-diols from pea weevils and cowpea weevils that have been shown to initiate callus formation on pea pods at extremely low application rates. Synthetic analogs have been prepared and examined to evaluate structural requirements for inducing this unusual neoplastic response. Chain length (optimum length C22–C24) is important, whereas unsaturation within the chain is relatively unimportant. Difunctionality is required for maximum activity, but the α,ω-diols themselves are inactive. Most critical is the ester portion(s) of the molecules; 3-hydroxypropanoate esters are far more active than any analogs examined.

Use of 1H-15N PEP-HSQC-TOCSY at natural abundance to facilitate the structure elucidation of naturally occurring peptides

Abstract The application of 1H-15N PEP-HSQC-TOCSY at natural abundance is demonstrated here on a 13 mM sample (0.048 mM 15N/position) of the biologically active linear tetradecapeptide bombesin (MW=1619.9) as a way to expedite the structural characterization of peptidic natural products.

A detailed mechanistic investigation into the reaction of 3-methylpentanoic acid with Meldrum's acid utilizing online NMR spectroscopy

A thorough investigation into the mechanism of the reaction of 3‐methylpentanoic acid and Meldrums acid using online NMR spectroscopy is reported. This study is an expansion of a previous analysis of this chemical transformation in the synthesis of an active pharmaceutical ingredient imagabalin. The 3‐methylpentanoic acid analogue reveals similar behavior under the reaction conditions. Online NMR spectroscopy and offline characterization experiments reveal new information about the mechanism, providing conclusive spectroscopic evidence for the previously hypothesized dimer anhydride intermediate species 3‐methylpentanoic anhydride as a productive intermediate. The presence of an acyl chloride intermediate species, 3‐methylpentanoyl chloride, is also revealed for the first time in this synthesis. Copyright

Chapter 10 Nuclear magnetic resonance spectroscopy

Publisher Summary This chapter focuses on nuclear magnetic resonance (NMR) spectroscopy, which is used to study the behavior of the nuclei in a molecule when subjected to an externally applied magnetic field. Nuclei spin about the axis of the externally applied magnetic field and consequently possess an angular momentum. The groups of nuclei most commonly exploited in the structural characterization of small molecules by NMR methods are the spin 1/2 nuclei, which include 1 H, 13 C, 19 F, and 31 P. NMR is amenable to a broad range of applications. It has found wide utility in the pharmaceutical, medical, and petrochemical industries as well as across the polymer, materials science, cellulose, pigment, and catalysis fields. The vast diversity of NMR applications may be because of its profound ability to probe both chemical and physical properties of molecules, including chemical structure and molecular dynamics. This gives NMR the potential to have a great breadth of impact compared with other analytical techniques. It can also be applied to liquids, solids, or gases.