Keith Clinch

A novel and simple colorimetric method for screening Giardia intestinalis and anti-giardial activity in vitro

A new and simple colorimetric method has been developed for determining activity in vitro against Giardia intestinalis. The microtitre plate assay is based upon the nucleoside hydrolase activity released from G. intestinalis by lysis. Action of the nucleoside hydrolase on the substrate analogue, 4-nitrophenyl beta-D-ribofuranoside (NPR), gives rise to a coloured product which may be determined directly by the change in absorbance. A number of other such nucleoside analogues can be similarly used, but NPR is the preferred substrate, since it gives high enzymic activity at a relatively low substrate concentration. The IC50 values determined using this method for the known anti-giardials metronidazole, tinidazole and furazolidone were consistent with previously published values. The method is simple, does not involve radioisotopes or complex instrumentation, and thus provides a convenient method for screening potential anti-giardial agents.

Transition state analogue inhibitors of human methylthioadenosine phosphorylase and bacterial methylthioadenosine/S-adenosylhomocysteine nucleosidase incorporating acyclic ribooxacarbenium ion mimics.

Several acyclic hydroxy-methylthio-amines with 3-5 carbon atoms were prepared and coupled via a methylene link to 9-deazaadenine. The products were tested for inhibition against human MTAP and Escherichia coli and Neisseria meningitidis MTANs and gave K(i) values as low as 0.23 nM. These results were compared to those obtained with 1st and 2nd generation inhibitors (1S)-1-(9-deazaadenin-9-yl)-1,4-dideoxy-1,4-imino-5-methylthio-D-ribitol (MT-Immucillin-A, 3) and (3R,4S)-1-[9-deazaadenin-9-yl)methyl]3-hydroxy-4-methylthiomethylpyrrolidine (MT-DADMe-Immucillin-A, 4). The best inhibitors were found to exhibit binding affinities of approximately 2- to 4-fold those of 3 but were significantly weaker than 4. Cleavage of the 2,3 carbon-carbon bond in MT-Immucillin-A (3) gave an acyclic product (79) with a 21,500 fold loss of activity against E. coli MTAN. In another case, N-methylation of a side chain secondary amine resulted in a 250-fold loss of activity against the same enzyme [(±)-65 vs (±)-68]. The inhibition results were also contrasted with those acyclic derivatives previously prepared as inhibitors for a related enzyme, purine nucleoside phosphorylase (PNP), where some inhibitors in the latter case were found to be more potent than their cyclic counterparts.

Synthesis of analogues of monic acids A and C: Potential herbicides and inhibitors of isoleucyl tRNA synthetase

Abstract The m-substituted benzene compounds 16–21 and biphenyl derivatives 25–27 have been synthesised as simplified analogues of monic acids A 3 and C 4. In addition the disubstituted 1,3-dioxanes 41–43 have been prepared and all compounds tested as herbicides and for their ability to inhibit spinach chloroplast isoleucyl tRNA synthetase.

(4R,5S)-4-Hy­droxy­meth­yl-5-[(methyl­sulfanyl)­meth­yl]-1,3-oxazolidin-2-one

The title compound, C6H11NO3S, crystallizes utilizing a three-dimensional set of O—H⋯O, N—H⋯O and C—H⋯O hydrogen bonds. The 1,3-oxazolidin-2-one ring adopts an envelope conformation with the C atom bearing the hydroxymethyl group as the flap.

tert-Butyl (2R,4aR,5aR,11aS,12R,12aR)-8-[bis­(tert-but­oxycarbon­yl)amino]-12-hydroxy-2-meth­oxy-2,10-dioxo-4,4a,5a,6,9,10,11,11a,12,12a-deca­hydro-2H-1,3,5-trioxa-6,7,9,11-tetra­aza-2λ5-phosphatetra­cene-6-carboxyl­ate methanol monosolvate monohydrate

The title compound, C26H40N5O13P·CH3OH·H2O, crystallizes with one water and one methanol molecule providing important crystal-binding interactions. The compound has the unusual feature of having two butoxycarbonyl groups bound to one N atom. The conventional attractive hydrogen bonds involving hydroxy, amine and water donors include bifurcations at both donors and acceptors with novel R 1 2(6) and R 2 1(6) motifs. These are supplemented by C—H⋯O interactions between adjacent molecules forming chain and R 2 2(10) ring motifs.

3-Benzoyl-5-chloro­uracil

The dihedral angle between the planes of two aromatic rings in the title compound [systematic name: 3-benzoyl-5-chloro-pyrimidine-2,4(1H,3H)-dione], C11H7ClN2O3, is 86.79 (6)°. Centrosymmetric dimers formed by N—H⋯O hydrogen bonds are linked through C—H⋯O interactions, forming a two-dimensional network parallel to (10).