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Fosinopril, a phosphinic acid inhibitor of angiotensin I converting enzyme: in vitro and preclinical in vivo pharmacology.

Fosinopril is the first member of a new chemical class of angiotensin I (AI) converting enzyme (ACE) inhibitors, the phosphinic acids. In vitro, SQ 27,519, the active moiety of the prodrug fosinopril, was a more potent inhibitor of purified rabbit lung ACE- (IC50 = 11 vs. 23 nM) and bradykinin-induced contractions of guinea pig ileum than captopril. In vivo, SQ 27,519 was equipotent to captopril as an inhibitor of an AI pressor response after intravenous (i.v.) administration to conscious rats and monkeys but appeared to be less potent in conscious dogs. After oral administration, fosinopril again was equipotent to captopril as an inhibitor of an AI pressor response in rats and monkeys and slightly less potent in dogs. However, both SQ 27,519 (i.v. studies) and fosinopril (oral studies) had a longer effect than captopril in all three species. When fosinopril was administered orally for 5 days, its effects on an AI pressor response were the same on days 1 and 5, suggesting lack of tolerance to the compound. The ACE inhibitory effect of captopril, but not fosinopril, was prolonged in conscious rats with glycerol-induced acute renal failure, suggesting that fosinopril is excreted by an extrarenal route. Finally, fosinopril had no effect on the pressor or chronotropic effects of norepinephrine (NE) or 1,1-dimethyl-4-phenylpiperinium (DMPP) or electrical stimulation of the sympathetic ganglia of pithed rats. Fosinopril attenuated the pressor, but not the chronotropic effects of tyramine. We conclude that fosinopril is a potent and long-lasting inhibitor of ACE in conscious animal models that does not impair adrenergic function or reflexes.(ABSTRACT TRUNCATED AT 250 WORDS)

Acute Kidney Injury↗

Determination of SQ 33,600, a phosphinic acid containing HMG CoA reductase inhibitor, in human serum by high-performance liquid chromatography combined with ionspray mass spectrometry.

A method for the determination of SQ 33,600 in human serum is presented. This compound, which contains both carboxylic and phosphinic acid functional groups, is an HMG CoA reductase inhibitor currently under clinical investigation at the Bristol-Myers Squibb Pharmaceutical Research Institute. Human serum extracts prepared using solid-phase techniques were analyzed by combining high-performance liquid chromatography and atmospheric pressure ionization mass spectrometry. Under the conditions of the analysis, SQ 33,600 and its fluorinated analog, SQ 33,547, used as the internal standard, existed as anions in solution and could be sampled directly using the ionspray technique. The method utilized a simple isocratic mobile-phase system. No sample derivatization was required for these polar molecules. The retention time of the analytes was 3.5 min with a total analysis time of 5 min. The limit of detection was 0.5 ng ml-1 serum with a minimum quantifiable limit of 2.0 ng ml-1. The method was linear to at least 400 ng ml-1.

Chromatography, High Pressure Liquid↗

Dearomatizing anionic cyclizations of N-benzyl-N-methyldiphenylphosphinamides. Synthesis of gamma-(N-methylamino)phosphinic acids.

The first dearomatizing anionic reaction of a phenyl ring promoted by an N-benzyl-N-methylphosphinamide group is described. The intermediate lithium species can be trapped with different electrophiles, affording tetrahydrobenzo[c]-1-aza-2lambda(5)-phospholes with excellent diastereoselectivity. The new process is a simple and very efficient entry to the stereoselective synthesis of functionalized gamma-(N-methylamino)phosphinic acids and esters.

Journal Article↗

Use of highly active palladium-phosphinous acid catalysts in Stille, Heck, amination, and thiation reactions of chloroquinolines.

An efficient synthetic route toward a variety of 2,4-disubstituted quinolines has been developed. Alkylation and arylation of 4-chloroquinoline using organolithium reagents proceed with high regioselectivity in position 2 under cryogenic conditions. The intermediate 1,2-dihydro-4-chloroquinoline derivatives are unstable to air and are easily oxidized to the corresponding 2-substituted 4-chloroquinolines in high yields. Highly active palladium-phosphinous acid catalysts POPd, POPd1, and POPd2 have been employed in Stille cross-couplings of quinaldine with arylstannanes and in Heck additions of various 2-substituted 4-chloroquinolines to tert-butyl acrylate. In particular, POPd combines high catalytic activity for cross-coupling reactions with simplicity of use due to its stability to air. Utilizing CsF in POPd-catalyzed Stille couplings further increased the reactivity of arylstannanes, which was attributed to the fluorophilicity of organotin compounds. Basic additives were found to exhibit a significant effect on the yields of the POPd-promoted Heck reactions. In general, dicyclohexylmethylamine affords superior results than NaOAc, Cs(2)CO(3), or t-BuOK. POPd was also found to tolerate amine and thiol substrates and proved to promote carbon-heteroatom bond formation of chloroquinoline derivatives with aliphatic and aromatic amines and thiols, respectively.

Journal Article↗

C6, C7, and C8 perfluoroalkyl-substituted phosphinic acids.

Reaction of red phosphorus with RfI in a 1:2 molar ratio at 230 degrees C led to the formation of a mixture of (Rf)2PI and (Rf)PI2 (Rf = C6F13, C7F15, C8F17) in about a 70:30 ratio, respectively. These mixtures were separated by vacuum distillation. (Rf)2PI (Rf = C6F13, C7F15) are yellow liquids whereas (C8F17)2PI is a yellow solid. Oxidation of (Rf)2PI with excess NO2 led to (Rf)2P(O)OH (Rf = C6F13, C7F15, C8F17) in > 90% isolated yields after aqueous hydrolysis of the anhydride intermediates. These highly fluorinated phosphinic acids are white solids with sharp melting points and are highly soluble in methyl sulfoxide (DMSO) and 1,1,2-trichlorotrifluoroethane. However, solubility in chloroform and methylene dichloride is low. These perfluoroalkylphosphinic acids were characterized by IR, NMR (1H, 19F, and 31P), and mass spectra and elemental analysis.

Journal Article↗

Inhibition of MMP-1 and MMP-13 with phosphinic acids that exploit binding in the S2 pocket.

Through the use of empirical and computational methods, phosphinate-based inhibitors of MMP-1 and MMP-13 that bind into the S2 pocket of these enzymes were designed. The synthesis and testing of 2 suggested that binding was occurring as hypothesized. Structure determination of a co-crystal of 2 bound to the catalytic domain of MMP-1 confirmed the binding mode. Substituents binding into S2, S1', S2' and S3', were optimized yielding compounds with low double-digit nM IC50's against these enzymes.

Binding Sites↗

Stereoselective separations of chiral phosphinic acid pseudodipeptides by CEC using silica monoliths modified with an anion-exchange-type chiral selector.

A nonaqueous CEC method for the simultaneous separation of the four stereoisomers of the N-benzyloxycarbonyl phosphinic pseudodipeptide methyl ester benzyloxycarbonyl-homophenylalanine Z-hPhepsi(PO2HCH2)Phe-OCH3 as well as of the corresponding N-2,4-dinitrophenyl (DNP)-derivative with free C-terminal carboxylic group DNP-hPhepsi(PO2HCH2)Phe-OH was developed. For this purpose, a monolithic silica capillary column modified with a cinchona alkaloid-derived anion-exchange-type chiral selector, namely O-9-(tert-butylcarbamoyl)quinidine (tBuCQD) was prepared. The mobile phase composition (ACN/methanol ratio, counterion type) was thoroughly optimized to end up with baseline resolution of all four stereoisomers with critical resolution of as high as about 2. The CEC method proved to be superior over the corresponding HPLC separations primarily due to significantly enhanced plate numbers (between 200,000 and 600,000 m(-1) in CEC). Diastereoselectivity contributions arising from electrophoretic mobility differences of the diastereomers facilitated the separation of the later eluted diastereomeric peak pair (peaks III and IV), but had a negative influence on the selectivity of the earlier eluted diastereomeric peak pair (peaks I and II). The stereoselective CEC assay allowed the assessment of the stereoisomeric purity of the individual isomers which were obtained by preparative HPLC on a CHIRALPAK QD-AX column that is based on the same tBuCQD selector. The present study demonstrates that there exist problems which are hard to solve by HPLC, yet can be conveniently solved by CEC. Moreover, it was intended to prove by this practical application that CEC with monolithic columns is robust enough to be used for solving real-life problems.

Anion Exchange Resins↗