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A series of ditopic ω-di(2-pyridylmethyl)amine carboxylic acid ligands incorporating a range of n-alkyl linkers (CnCOOH, n = 3–5, 7, 10 and 11) have been synthesised. Solution phase studies showed a 1 : 1 coordination stoichiometry between the ligands and M(ClO4)2·6H2O (M = ZnII or CuII) in all cases. The ZnII and CuII complexes were subsequently crystallised by liquid–liquid diffusion and the solid-state structures investigated by X-ray crystallography. The crystal structures obtained are entirely consistent with the 1 : 1 metal–ligand ratio of the solution-phase adducts. However, the coordination geometries and complex topologies are dependent on the alkyl chain length of the ligand CnCOOH. The ZnII and CuII complexes of the short alkyl chain ligands (n ≤ 5) exhibit 1D coordination polymeric structures with somewhat different conformations for {[Zn(C3COO)(H2O)](ClO4)·3.5H2O}n (1), {[Zn(C4COO)(H2O)]4(ClO4)4·1.5H2O}n (2), {[Zn(C5COO)(H2O)](ClO4)}n (3), {[Cu(C3COO)](ClO4)·MeOH}n (4), {[Cu(C4COO)(H2O)]2(ClO4)2·2H2O}n (5) and {[Cu(C5COO)(H2O)](ClO4)·2H2O}n (6). In contrast, the ligands with longer alkyl chains (n ≥ 7) participate in Zn2L2 metallomacrocyclic structures {[Zn(C7COO)(H2O)](ClO4)}2 (7), [Zn2(C10COO)2(H2O)2](ClO4)2·2H2O·MeOH (8) and {[Zn2(C11COO)2(H2O)2][Zn2(C11COO)2](ClO4)4·H2O}n (9). The formation of metallomacrocycles instead of the 1D coordination polymers is a persistent trend and, with identical crystal growth conditions and a non-coordinating anion employed, appears to be an effect of the longer alkyl chain.

Reaction of (S)-2-chloro-3-phenylpropanoic acid derivatives with NBS gave the corresponding 3-bromo-2-chloro derivatives with a preference for the formation of the (2R,3S) isomers over the (2R,3R) isomers. The stereoselectivity was affected by the nature of the carboxylic acid derivative. Reaction of ester derivatives was highly stereoselective while the reaction of amide derivatives showed varied stereoselectivity which depended on the nature of the amide. Theoretical studies at UHF/3-21G* level showed that the intermediate benzylic radical of the methyl ester, the methyl amide and the diisopropyl amide derivatives had different energy profiles with respect to rotation of the C2–C3 bond. The different stereoselectivity observed from reaction of the various acid derivatives could be attributed, at least in part, to different distribution of conformers of the radical intermediate.

Two progressive series of molecules with two polyhydroxybenzamide substructures were synthesized and tested as potential inhibitors of catechol-O-methyltransferase (COMT). These compounds were designed for the purpose of enhanced enzyme binding with duplicated substructures separated by a linker section of various lengths. Our results show that potency and mode of inhibition observed with the "bifunctional" compounds were a reflection of their bifunctional nature. Furthermore, potency and mode of inhibition were dependent on the length of the linker section. Of the assayed compounds, the optimum linker was found to be diaminopropane. For example, N,N'-1,3-propanediylbis(3,4-dihydroxybenzamide) and N,N'-1,3-propanediylbis(3,4,5-trihydroxybenzamide) demonstrated strong inhibitory action against COMT, with apparent Ki values of 0.3 and 6.0 microM, respectively.

The stereochemistry at position 2 of the title compound, C 14 H 17 BrO 4 , has been confirmed as S.

Proteins from eucaryotic cells which have a carboxyl-terminal CAAX motif are posttranslationally modified by isoprenylation. The pathway involves the linkage of an all-trans-farnesyl (C15) or an all-trans-geranylgeranyl (C20) moiety to the cysteine residue followed by proteolysis which generates the modified cysteine as the carboxyl-terminal residue. Carboxylmethylation of the modified cysteine residue completes the pathway. This latter methylation reaction is the only potentially reversible reaction in the pathway and thus of possible regulatory significance. A specific esterase is required to reverse the methylation. It is demonstrated here that simple isoprenylated cysteine derivatives, such as N-acetyl-S-farnesyl-L-cysteine methyl ester (L-AFCM) and N-acetyl-S-geranylgeranyl-L-cysteine methyl ester (L-AGGCM), are substrates for a rod outer segment (ROS) membrane esterase activity. The KM and Vmax values for L-AFCM and L-AGGCM are 186 microM and 2.2 nmol mg-1 min-1 and 435 microM and 4.8 nmol mg-1 min-1, respectively. The enzyme(s) is stereoselective rather than stereospecific because D-AFCM is enzymatically hydrolyzed with KM and Vmax values of 157 microM and 0.46 nmol mg-1 min-1, respectively. The enzyme(s) does not process N-acetyl-L-cysteine methyl ester, demonstrating that the isoprenyl moiety is required for substrate activity. Ebelactone B is a potent mechanism-based inactivator of the enzyme with a KI = 42 microM and a kinh = 3.7 x 10(-3) s-1. Importantly, L-AFCM, L-AGGCM, and ebelactone B all inhibit the demethylation of the endogenous ROS substrates, showing that the same enzymatic activity is involved in the processing of the synthetic and physiological substrates.

Structure-activity studies were performed on the retinal rod outer segment isoprenylated protein methyltransferase that transfers a methyl group from S-adenosylmethionine (AdoMet) to the carboxyl group of isoprenylated (farnesylated or geranylgeranylated) cysteine residues. This methyltransferase enzyme has been shown to methylate N-acetyl-S-farnesyl-L-cysteine (L-AFC, 1) and S-(farnesyl-3-thio)propionic acid (FTP, 2). It is shown here that the enzyme does not enzymatically process D-AFC (8), although D-AFC (8) is a mixed-type inhibitor of the enzyme

The free-radical reactions of a range of amino acid derivatives with N-bromosuccinimide are described. The products and relative rates of these reactions indicate that the α-position of an N-phthaloyl-substituted α-amino acid derivative is much less reactive than that of a corresponding N-acyl amino acid derivative toward hydrogen atom transfer. This is attributed to the proactive effects of acylamino and carboxyl substituents, in contrast to the counteractive effects of phthalimido and carboxyl groups. The reactions exemplify procedures for the regiocontrolled functionalization of amino acid and peptide derivatives. © 1991, American Chemical Society. All rights reserved.

Bifunctional compounds were tested in vitro as potential inhibitors of pig liver catechol-O-methyltransferase (COMT) with respect to the catechol substrate 4-[(3,4-dihydroxyphenyl)azo]benzenesulfonate. The bifunctional compounds were a composite of either two nitrocatechols or one nitrocatechol and one phenol, linked by amide bonds to a spacer unit comprising two to five methylene groups. The unsymmetrical compounds N-[2-(4-hydroxybenzoylamine)ethyl]-3,4-dihydroxy-5-nitrobenzamide], N-[3-(4-hydroxybenzoyl-amine)propyl]-3,4-dihydroxy-5-nitrobenzamide] and N-[5-(4-hydroxybenzoylamine)pentyl]-3,4-dihydroxy-5-nitrobenzamide] demonstrated strong inhibitory action against COMT with K(i) values in the 100 nM range. In comparison, the monofunctional nitrocatechol analogues of these compounds had K(i) values that were significantly higher.

The title compound, C 17 H 14 O 5 , was obtained as a byproduct from a procedure to regioselectively hydroxylate homochiral acid derivatives. Structural analysis confirmed its identity and showed it to be achiral.

Structural analysis of trans-3-bromo-2-chloro­indan-1-one, C9H6BrClO, confirms the relative stereochemistry of the Cl and Br atoms.

The stereochemistries at positions 2 and 3 of the title compounds, C15H21BrClNO, (I), and C15H12BrClN2O3, (II), have been confirmed by X-ray structural analysis. The halogen atoms adopt an antiperiplanar arrangement in each case.

The stereochemistry at position 2 of the title compound, C 14 H 17 BrO 4 , has been confirmed as S.