Preparation and antimicrobial activity of micacocidin

Micacocidin (3), a Zn-free derivative of micacocidin A (1), was prepared to evaluate its antimicrobial activity in comparison with 1 and to obtain a starting material for chemical modification of 1. The structure of 3, quite unlike those of any previously known antimicrobial agents, was elucidated by 1-D and 2-D homonuclear and heteronuclear NMR and mass spectroscopy. Micacocidin (3) thus prepared exhibited weak or no antibacterial activity except against Mycoplasma species, i.e. 3 showed stronger activity than 1. It is noteworthy that 3 displayed high activity against fungi such as Candida, Aspergillus and Trichophyton species.

Micacocidin A, B and C, novel antimycoplasma agents from Pseudomonas sp. II. Structure elucidation

Metal-containing novel heterocyclic antibiotics, micacocidin A (1), B (2), and C (3) have been isolated from the culture filtrate of Pseudomonas sp. No. 57-250. The structure and absolute configuration of micacocidin A, an octahedral Zn2+ complex, was determined by X-ray crystallographic analysis. And then, the structures of the two congeners, micacocidin B (Cu2+ complex) and C (Fe3+ complex) were investigated by employing one dimensional and two dimensional homonuclear and heteronuclear NMR spectroscopies and mass spectrometry.

Endothelin receptor antagonist triterpenoid, myriceric acid A, isolated from Myrica cerifera, and structure activity relationships of its derivatives

As the first non-peptide endothelin receptor antagonist from a higher plant, a new triterpenoid, myriceric acid A (50-235) (1) was isolated from the bayberry, Myrica cerifera. Myriceric acid A (1) inhibited not only an endothelin-1-induced increase in cytosolic free Ca2+ concentration (IC50 = 11 +/- 2 nM) but [125I]endothelin-1 binding in rat aortic smooth muscle cells (Ki = 66 +/- 15 nM). Two new related triterpenoids, myriceric acid C (6), and myriceric acid D (8), were also isolated. Furthermore, the chemical modification of these natural products led to the synthesis of sulfated derivatives (13, 14, 15) which showed 1.5 to 20 times higher affinity for endothelin receptors. The structure activity relationships of myriceric acids and their derivatives are discussed.

Synthesis of manool-related labdane diterpenes as platelet aggregation inhibitors

Enantioselective total synthesis of the labdane diterpene (-)-1, was achieved starting from the R-(-)-enantiomer of the Wieland-Miescher ketone. The enantiomer (+)-1 was obtained by partial synthesis via microbial transformation of sclareol. These results established that the natural compound (+)-1, a platelet aggregation inhibitor, has a normal absolute stereochemistry like that of manool. The B-norlabdane-related compound 44 was also synthesized using a novel ring contraction reaction.

Structures of new peptide antibiotics, plusbacins A1-A4 and B1-B4

The constituent amino acids of plusbacins A1-A4 were determined to be two moles of L-trans-3-hydroxyproline and one mole each of D-threo-beta-hydroxyaspartic acid, L-threo-beta-hydroxyaspartic acid, D-allo-threonine, D-serine, D-alanine and L-arginine. In plusbacins B1-B4, one mole of L-trans-3-hydroxyproline is replaced by L-proline. The fatty acid residue of A1 and B1 was determined to be 3-hydroxy-tetradecanoic acid, for A2 and B2 to be 3-hydroxy-isopentadecanoic acid, for A3 and B3 to be 3-hydroxy-isohexadecanoic acid, and for A4 and B4 to be 3-hydroxy-hexadecanoic acid. A lactone linkage was suggested to reside between L-threo-beta-hydroxyaspartic acid and 3-hydroxy-fatty acid residues by degradation experiments. The amino acid sequences of plusbacins A2 and B2 were confirmed by Edman degradation of their deacylated products, and supported by mass spectrometric studies. From the above, structures of all components of plusbacins were concluded.

Structure determination of a diuretic-glutathione conjugate by mass and n.m.r. spectrometry

1. A glutathione (GSH) conjugate of the uricosuric diuretic DBCA 6,7-dichloro-5(N,N-dimethylsulphamoyl)-2,3-dihydrobenzofuran-2-car boxylic acid, formed enzymically in rat liver 100,000g supernatant fortified with GSH, was purified by t.l.c. and h.p.l.c. 2. According to mass spectrometry the composition of the GSH-conjugate corresponded to C21H29N4O11S2Cl2. 1H- and 13C-n.m.r. studies gave the structure of the conjugate as 2-glutathionyl-3-[3,4-dichloro-5-(N,N-dimethyl sulphamoyl)2-hydroxyphenyl]-propionic acid, which indicates that GSH was bound to the chiral centre carbon and caused scission of the C-O bond in the dihydrofuran ring.

Glutathione conjugation of synthetic steroids in isolated rat hepatocytes

When designing steroid drugs with multiple double bonds, the influence of glutathione conjugation on the pharmacodynamics of drug action should be considered. We have examined the effect of canrenone, a mineralocorticoid receptor antagonist, on isolated rat hepatocytes and found that 1 mM canrenone injured the hepatocytes during shortterm incubation at 37 C, while an analogue of canrenone which bears 4 double bonds (delta 1,11-CAN) did not manifest such toxicity. To further pursue this, we prepared testosterone analogues comprising multiple double bonds as model compounds, and incubated them with freshly isolated rat hepatocytes. The viability of the hepatocytes was not influenced by any of the steroids, but some of them having a double bond at the C6-C7 position reduced the cellular glutathione levels. This was found to be due to conjugation of glutathione to the C7 position of the steroid molecule, and the rate of conjugation was accelerated when an additional double bond was introduced at C1-C2 or C11-C12 positions. The finding is interesting as glucuronidation or sulfation are common as conjugation processes of steroids.

Metabolism of the antimycotic agent, croconazole, in rabbits

The biotransformation of croconazole, a potent new antimycotic agent, was studied in the rabbit. Croconazole was excreted in the urine primarily as conjugates. Most of the radioactive metabolites in the urine could be extracted with organic solvent after hydrolysis with beta-glucuronidase. As many as 16 metabolites in the organic extracts were separated by TLC. Thirteen were identified by comparison of their mass and/or proton NMR spectra with those of synthetic samples. Aromatic ring hydroxylation of each benzene ring, O-dechlorobenzylation, and loss of the imidazole ring were found to occur.

N-hydroxymethyl metabolites of 450191-S, a 1H-1,2,4,-triazolyl benzophenone derivative, in dog plasma

In a metabolic experiment of 5-[(2-aminoacetamido)methyl]-1-[4-chloro-2-(o-chlorobenzoyl)phenyl ]-N, N-dimethyl-1H-1,2,4,-triazole-3-carboxamide hydrochloride dihydrate (450191-S) in dogs, two new metabolites 8-chloro-6-(o-chlorophenyl)-N-hydroxymethyl-4H-1,2,4-triazolo [1,5-a] [1,4]benzodiazepine-2-carboxamide (M-A) and 8-chloro-6-(o-chlorophenyl)-N-hydroxymethyl-N-methyl-4H-1,2,4-triazolo [1,5-a] [1,4]benzodiazepine-2-carboxamide (M-D) in plasma were found in addition to 8-chloro-6-(o-chlorophenyl)-N,N-dimethyl-4H-1,2,4-triazolo[1,5-a] [1,4] benzodiazepine-2-carboxamide (M-1), 8-chloro-6-(o-chlorophenyl)-N-methyl-4H-1,2,4-triazolo[1,5-a] [1,4] benzodiazepine-2-carboxamide (M-2), 8-chloro-6-(o-chlorophenyl)-4H-1,2,4-triazolo-[1,5-a] [1,4] benzodiazepine-2-carboxamide (M-3), and 8-chloro-6-(o-chlorophenyl)-4H-1,2,4-triazolo[1,5-a] [1,4] benzodiazepine-2-carboxylic acid (M-4). The structures of N-hydroxymethyl metabolites were elucidated mainly by mass spectrometry. The structures were confirmed by synthesizing the authentic compounds and comparing the mass spectra.

PB-5266 A, B and C, new monobactams. II. Physico-chemical properties and chemical structures

The chemical structures of three new monobactams, PB-5266 A, B and C, were elucidated by their physico-chemical properties and spectrometric studies. In contrast to previously described monobactams, they all possess a dehydroasparagine residue.