James A. Matson

Discovery of antitumor indolocarbazoles: rebeccamycin, NSC 655649, and fluoroindolocarbazoles.

A fermentation directed product search for potential anticancer drugs conducted by Bristol-Myers in the 1970s and early 1980s resulted in the identification of a novel indolocarbazole (IC) rebeccamycin (RBM) as a potential drug development candidate. Subsequently, an analog program designed to impart distal site in vivo antitumor activity resulted in the discovery of diethylaminoethyl analog of RBM (DEAE-RBM), which is presently undergoing clinical evaluation as NSC 655649 and BMY-27557. Strong DNA intercalation is the primary mechanism of action of DEAE-RBM resulting in the potent catalytic inhibition of both topoisomerases I and II. Precursor feeding fermentation experiments with fluorine-substituted tryptophans yielded novel fluoroindolocarbazoles (FICs). These FICs were identified as targeting topoisomerase (topo) I in a mechanism-based screen and their action on topo I was confirmed by production of topo I-mediated single-strand breaks in DNA at sites essentially identical to those induced by camptothecin. Topo I dependent cytotoxicity was demonstrated for specific FICs using a P388 and camptothecin-resistant P388/CPT45 pair of cell lines, the latter expresses little or no functional topo I. For example, topo I selectivity was greatest with 3,9-difluoro substituted FIC and was least significant and least cytotoxic with 4,8-difluoro substituted FIC. The review focuses on the discovery of the rebeccamycin class of compounds and their structure-activity relationships leading to the development of the clinical candidate BMY-27557 (NSC 655649), as well as the lead identification of the fluoroindolocarbazole class of compounds.

Synthesis and activity of a C-8 keto pleuromutilin derivative

A C-8 keto pleuromutilin derivative has been synthesized from the biotransformation product 8-hydroxy mutilin. A key step in the process was the selective oxidation at C-8 of 8-hydroxy mutilin using tetrapropylammonium perruthenate. The presence of the C-8 keto group precipitated interesting intramolecular chemistry to afford a compound (10) with a novel pleuromutilin-derived ring system.

Sordarin oxazepine derivatives as potent antifungal agents

The synthesis and biological activity of sordarin oxazepine derivatives are described. The key step features a regioselective oxidation of an unprotected triol followed by double reductive amination to afford the ring-closed products. The spectrum of antifungal activity for these novel derivatives includes coverage of Candida albicans, Candida glabrata, and Cryptococcus neoformans.

Analysis of amino acid enantiomers derived from antitumor antibiotics using chiral capillary electrophoresis.

The chiral separation of enantiomeric forms of derivatized amino acids have been achieved based on a metalchelate chiral capillary electrophoretic method and a cyclodextrin mediated host-guest interaction approach in micellar electrokinetic chromatography (MEKC) mode with laser-induced fluorescence detection. This approach has been applied to the determination of enantiomeric forms of amino acids derived from novel depsipeptide antitumor antibiotics, BMY-45012 and its analogs. Amino acids were analyzed by complete hydrolysis and the hydrolysate was derivatized with either dansyl chloride for UV absorbance detection or fluorescein isothiocyanate for laser based fluorescence detection. The presence of several amino acids, serine and beta-hydroxyl-N-methy-valine in the proposed structure have been confirmed as D-serine and L-beta-hydroxyl-N-methy-valine enantiomeric forms by both chiral capillary electrophoresis (chiral CE) and MEKC approaches. A non-chiral amino acid, sarcosine, was also confirmed. These methodologies provide a quick and sensitive approach for the determination of amino acids racemization of pharmaceutical natural products and have proven to be useful for structural elucidation refinement.

Kedarcidin chromophore: Structure elucidation of the amino sugar kedarosamine

Abstract The structure of kedarosamine, the amino sugar moiety of kedarcidin chromophore, was established by NMR spectroscopy and X-ray crystallography as 2,4 dideoxy-4-(dimethylamino)-L-fucopyranose. bl

Korkormicins, novel depsipeptide antitumor antibiotics fromMicromonospora sp C39500: Fermentation, precursor directed biosynthesis and biological activities

Micromonospora sp C39500, isolated in our laboratory from a soil sample, produced a complex of seven novel depsipeptide antitumor antibiotics, designated korkormicins. The major component of the complex, korkormicin A, has a MW of 1452 and a molecular formula of C66H84N16O22. Korkormicin A exhibits potentin vivo antitumor activity against P388 leukemia and M109 lung carcinoma implanted intraperitoneally (ip) in mice, with effective doses of 0.05–0.20 mg kg−1 injection−1, for five or three ip injections, respectively. It is also active against Gram-positive bacteria but inactive against Gram-negative bacteria. The production of korkormicin A was enhanced by 3-fold when 0.1%l-valine was added to the production culture at 48h. A titer of 401.0 μg ml−1 was achieved in the fermenter culture supplemented with 0.1%l-valine.

Partially Purified Grammostola Spatulata Venom Inhibits Stretch Activated Calcium Signaling in Bladder Myocytes and Improves Bladder Compliance in an In Vitro Rat Whole Bladder Model

PURPOSEnStretch activated nonselective cationic channels (SACs) are present in urinary bladder myocytes and thought to be activated during bladder filling. We investigated the relationship of stretch induced calcium signaling inhibition in bladder myocytes and bladder compliance modulation in an in vitro whole bladder model.nnnMATERIALS AND METHODSnGrammostola spatulata venom (SpiderPharm, Yarnell, Arizona) was purified by preparative high performance liquid chromatography. The resulting fractions were examined for their ability to inhibit the swelling activated intracellular free Ca2+ signal in cultured bladder myocytes. An in vitro rat whole bladder model was used to examine the effect of venom fractions on compliance, emptying and spontaneous contractions during bladder filling.nnnRESULTSnThe gadolinium ion, a SAC inhibitor, and venom fractions caused concentration dependent inhibition of the swelling activated intracellular free Ca2+ signal in bladder myocytes. When tested in a rat isolated whole bladder model, 0.1 and 0.2 mg./ml. partially purified venom produced a significant improvement in compliance (p <0.05), caused significant inhibition of the frequency of spontaneous bladder contractions (mean +/- SEM 35.8% +/- 3.7% and 62.3% +/- 4.4%, respectively, p </=0.001) and significantly reduced spontaneous bladder emptying, that is emptying in the absence of exogenous stimulation (38.8% +/- 5.6% and 43.9% +/- 2.5%, respectively, p </=0.0008). However, it produced little or no inhibition of carbachol induced bladder emptying.nnnCONCLUSIONSnOur data suggest that the activation of stretch induced signaling in bladder myocytes may have an important role in myogenic regulation of bladder contractility during bladder filling. Inhibition of SACs may improve bladder compliance.

Improved processes for the production and isolation of dynemicin A and large-scale fermentation in a 10000-liter fermentor

SummarySupplementing the culture ofMicromonospora chersina sp. nov. No. M956-1 with NaI (0.5 mg/l) enhanced the production of dynemicin A by 35-fold in shake flask culture. Homogeneous dynemicin A was obtained from the whole broth extract by Dicalite chromatography, Sephadex LH-20 chromatography and vacuum liquid chromatography. Gram quantities of dynemicin A were obtained from the fermentation ofM. chersina sp. nov. No. M956-1 in a 10000-liter fermentor.

Core-modified sordaricin derivatives: synthesis and antifungal activity.

Core-modified sordaricin derivatives were prepared via biotransformation followed by chemical modification and tested for antifungal activity. The antifungal activity proved to be very sensitive to modifications in the sterics and/or lipophilicity of the diterpene skeleton. Introduction of polar groups such as hydroxyl in the diterpene core results in loss of potency while small and lipophilic groups such as fluorine and the 7,8-olefin are well tolerated.