A series of 6-carboxyalkyl and 6-phosphonoxyalkyl derivatives of 7-oxo-8-D-ribityllumazine were synthesized as inhibitors of both Escherichia coli riboflavin synthase and Bacillus subtilis lumazine synthase. The compounds were designed to bind to both the ribitylpurine binding site and the phosphate binding site of lumazine synthase. In the carboxyalkyl series, maximum activity against both enzymes was observed with the 3'-carboxypropyl compound 22. Lengthening or shortening the chain linking the carboxyl group to the lumazine by one carbon resulted in decreased activity. In the phosphonoxyalkyl series, the 3'-phosphonoxypropyl compound 33 was more potent than the 4'-phosphonoxybutyl derivative 39 against lumazine synthase, but it was less potent against riboflavin synthase. Molecular modeling suggested that the terminal carboxyl group of 6-(3'-carboxypropyl)-7-oxo-8-D-ribityllumazine (22) may bind to the side chains of Arg127 and Lys135 of the enzyme. A hypothetical molecular model was also constructed for the binding of 6-(2'-carboxyethyl)-7-oxolumazine (15) in the active site of E. coli riboflavin synthase, which demonstrated that the active site could readily accommodate two molecules of the inhibitor. 相似文献
Dichloro-2,3,3-trimethyl-1-platinocyclobutane, , prepared by the metathetical reaction of Zeise's dimer and 1,1,2-trimethylcyclopropane, reacts with pyridine in chloroform to produce a platinum complex of 2,3-dimethyl-1-butene . Reaction of I with pyridine at low temperatures (ca. ?40° C) leads to a pyridine addition compound (III) in which the platinocyclobutane ring remains intact. The thermal isomerization of III, which may be conveniently studied using NMR, produces a mixture of II and the free olefin. 相似文献
The proton and carbon-13 nmr spectra of thioxanthone sulfoxide, thioxanthone sulfone, thioxanthonium bis(carbomethoxyl)methylide and thioxanthonium bis(carbomethoxyl)methylide S-oxide are assigned using 2-D nmr techniques and compared to those of thioxanthone. The pseudo-equatorial methylide fragment shields C4a/5a by ? 11 ppm relative to the corresponding sulfoxide and by ? 4 ppm relative to thioxanthone. The pseudo-axial methylide fragment in the oxysulfonium ylide has the same effect upon C4a/5a as does the pseudo-axial oxygen of the corresponding sulfone. The sulfoxide and the sulfonium ylide have similar chemical shifts for C2/7 (? 131 ppm) as do the sulfone and oxysulfonium ylide (? 133 ppm). 相似文献
Here we give an algorithm for finding the normal form of formal power series vector fields on
2n whose linear terms are the nilpotent matrix made up of 2 × 2 Jordan blocks. The problem is reduced to finding the Stanley decomposition of a bracket algebra, which is then determined using a straightening algorithm. The 4- and 6-dimensional cases are explicitly worked out. 相似文献
Electrospray ionization (ESI) mass spectrometry was employed to obtain both molecular weight confirmation and structural information for a series of novel alkenyldiarylmethane (ADAM) analogs. The mass spectral data were intended for use during the structure elucidation of ester hydrolysis products formed during an in vitro metabolism study of a series of novel ADAM analogs. The data on the precursor molecules show the presence of the molecular ion peak, [M+H](+), as well as a peak consistent with the hydrolysis product of the original ester ([MH-ROH+H(2)O](+)). However, chemical ionization mass spectrometry, elemental analysis and (1)H NMR data indicated the presence of only the intact diester compounds, suggesting that the formation of the hydrolysis product was an instrumental artifact, i.e., in-beam hydrolysis during ESI or a result of longer ion residence times of the ion trap mass analyzer. 相似文献