Halohydrocarbon synthesis by bromoperoxidase.

An enzyme extracted from marine red algae, Bonnemaisonia hamifera, is capable of incorporating bromine into a number of organic substrates in the pH range 5 to 8. At pH 7.3, incubation of partially purified preparations of bromoperoxidase with hydrogen peroxide, bromide ion, and 3-oxooctanoic acid leads to the formation of three volatile brominated hydrocarbons: dibromomethane, bromoform, and 1-pentyl bromide. The presence of significant quantities of halometabolites including volatile halohydrocarbons in marine organisms, ocean waters, and the upper atmosphere may result from peroxidase-catalyzed halogenation reactions.

Evaluation of the side arm of (naphthylvinyl)pyridinium inhibitors of choline acetyltransferase.

A number of quaternary salts of trans-4-(beta-1-naphthylvinyl)pyridine (NVP) were synthesized and evaluated as inhibitors of the enzymes choline acetyltransferase (ChAT) and acetylcholinesterase (AChE). Structural variations in the side arm attached to the pyridine nitrogen atom demonstrate that an inductive effect is small but significant for activity. Inhibition of ChAT by alkylated derivatives decreases when electron-withdrawing groups are placed in the side chain. Substitution of a methyl group on the pyridine ring only slightly affects activities toward ChAT and AChE. When the pyridinium moiety is replaced by an imidazolium ring, no ChAT inhibition was observed. The imidazolium compound, however, was a weak inhibitor of AChE. For design of affinity columns for purification of ChAT, the data also supports the use of long chain alkylated amide derivatives of NVP.

Structural correlations of choline acetyltransferase inhibitors: trans-N-(carboxymethyl)-4-(beta-1-naphthylvinyl)pyridinium bromide and cis-N-(2-aminoethyl)-4-(beta-1-naphthylvinyl)-3-methylpyridinium bromide hydrobromide.

This paper correlates the X-ray structures of two 4-(beta-1-naphthylvinyl)pyridine analogues (one cis and one trans) with chemical and biological activity data for this class of cholineacetylase inhibitors. Our results suggest that one of the two proposed mechanisms for inhibition by this class of compounds better describes their efficacy. Previous arguments about coplanarity of the aromatic rings and nucleophilicty across the vinyl linkage need to be modified. Quantum calculations are also included and substantiate previous suggestions about the charge distribution across the vinyl linkages. An alternate new mechanism of inhibition is proposed to encompass the published data and more recent results discussed in this paper.

Inactivation of gamma-glutamylcysteine synthetase by SAPH-3 disulfide: role of the histaminyl moiety.

Certain disulfide analogues of cystamine were prepared and evaluated for the ability to inhibit gamma-glutamylcysteine synthetase (GCS), the rate-limiting enzyme in glutathione synthesis. The compound SAPH-3 disulfide (2a) was found to be the most effective inactivator of GCS reported to date. Studies of structural analogues of 2a indicate that the histamine moiety plays a significant role in enzyme inactivation. Substitution of methyl groups on the carbon atoms adjacent to both sulfur atoms of the disulfide drastically decreases inhibitory action, probably due to a steric repulsion near the sulfur atom at the enzyme active site.

Synthesis and anti-cancer activity of 2-alkylaminomethyl-5-(E)-alkylidene cyclopentanone hydrochlorides.

A series of 2-alkylaminomethyl-5-(E)-alkylidene cyclopentanone hydrochlorides (2), have been synthesized and evaluated as anti-cancer agents. These compounds were designed as masked alpha-methylenecyclopentanones, which appear in many cytotoxic or anti-cancer natural products. Most of the synthesized compounds were found to be active towards various human cancer cell lines and many showed significant subpanel selectivity. For compounds containing the same alkylidene moiety (from C3 to C9), the dimethylaminomethyl analogs were more active than structures possessing morpholino-, pyrrolidino-, or piperidino-methyl groups. Alteration of the alkylidene moiety had little effect on anti-cancer potency. The mass spectrum of a glutathione adduct of 2h indicated that the mechanism of action for these anti-cancer agents may be related to the attack at the aminomethyl carbon atom by biological nucleophilic thiols.

Synthesis and cytotoxic activities of the amine-exchange products of 2-dimethylaminomethyl-5-(E)-substituted arylidene cyclopentanones with anilines: 2-arylaminomethyl-5-(E)-arylidene cyclopentanones.

A series of 2-arylaminomethyl, and 2-(4-morpholinylmethyl)-5-(E)-arylidene cyclopentanones have been synthesized via an amine-exchange reaction. Most of the compounds showed significant cytotoxic activities, in vitro, on various human cancer cell lines. Generally, compounds with a para-chloroanilino moiety were more active than those of other aniline derivatives. No apparent changes were observed by altering the substituents on the arylidene portion. For the majority of active compounds, leukemia is one of the most sensitive subpanels at both GI50 and TGI levels but the least sensitive one at the LC50 level. Colon cancer is one of the most sensitive subpanels in all three levels. COMPARE results indicated that the characteristics, and possibly the mechanism of the cytotoxic properties of the 2-arylaminomethyl derivatives might be different from that of the 2-dialkylaminomethyl derivatives previously reported.

Synthesis, antiinflammatory, and cytotoxic activities of 2-alkyl and 2-benzyl-2-dimethylaminomethyl-5-(E)-arylidene cyclopentanone hydrochlorides.

PURPOSE: A series of 2-substituted-2-dimethylaminomethyl-5-(E)-arylidene cyclopentanones, 4 were synthesized. The main objective of this investigation was to explore the structural parameters necessary for antiinflammatory activity in this series of compounds, while keeping cytotoxic action to a minimum. METHODS: The target compounds were synthesized in two steps commencing with 2-alkyl-cyclopentanones. Antiinflammatory, analgesic and cytotoxic activities were determined in rats. Cytotoxic results were examined in human cell lines. RESULTS: Eight of the eighteen synthetic substances possessed significant antiinflammatory activity and twelve showed appreciable analgesic action. Cytotoxicity was minimal or non-existent for most of the compounds. The stability of one of the compounds, 4b in both aqueous and non-aqueous media, and an amine exchange reaction with aniline were used to explain the observed antiinflammatory and cytotoxic activities. CONCLUSIONS: Unlike monosubstituted aminomethyl groups (Mannich bases) at the 2-position of 5-arylidene-2-cyclopentanones, a second substituent at the 2-position increases stability of the Mannich base and significantly decreases cytotoxic activity. Antiinflammatory and analgesic action is retained in many of the compounds, thus strongly indicating that these desired pharmacological results can be obtained without untoward damage to cells.

Structural studies on the inactivation of gamma-glutamylcysteine synthetase by the disulphide analogues of radioprotective cysteamine derivatives. Effects of aminoalkyl and hydroxyalkyl chain length and beta beta-bis-dimethylation.

Disulphide compounds have been shown to inactivate gamma-glutamylcysteine synthetase, the rate-limiting enzyme for GSH synthesis. Such compounds bind to a cysteine residue at or near the glutamate-binding site of the enzyme. This phenomenon is thought to be responsible for the synergistic toxicity of the thiophosphate radio- and chemo-protective agent WR2721 and the oxygen-radical generator 6-hydroxydopamine (2,4,6-trihydroxyphenethylamine). 6-Hydroxy-dopamine enhances conversion of WR2721 into its disulphide metabolite NN'-bis-(3-aminopropyl)cystamine, which, in turn, paralyses the synthetase. In an effort to identify radio- and chemo-protective thiols and thiol derivatives that do not have this toxicity, we have begun to define the structure-activity relationship that governs inactivation of the enzyme by analogues of WR2721 disulphide. NN'-Bis(aminoalkyl)cystamines and bis(hydroxyalkyl)cystamines with an alkyl chain length of C5 or greater are not inactivators of the synthetase. That this is not due solely to the size of these compounds is shown by the potent inactivation of the enzyme by SAPH3 disulphide, an extremely bulky cystamine analogue. beta beta-Bis-dimethylation of the cystamine portion of the molecule also obviates inactivation. This is almost certainly due to steric interference with disulphide interchange. These findings may facilitate the safe adjunctive use of the thiol counterparts of such compounds with oxygen-radical-generating chemotherapeutic agents, and may shed light on the structure of the region of the synthetase adjacent to the glutamate-binding site.