Discovery of new orally active prostaglandin D2 receptor antagonists.

To identify an orally available drug candidate, a series of 3-benzoylaminophenylacetic acids were synthesized and evaluated as prostaglandin D(2) (PGD(2)) receptor antagonists. Some of the compounds tested were found to exhibit excellent inhibitory activity against cAMP accumulation in human platelet rich plasma (hPRP), which is one of the indexes of DP antagonism. The optimization process including improvement of the physicochemical properties such as solubility, which may result in an improved pharmacokinetic (PK) profile, is presented. Optimized compounds were studied for their pharmacokinetics and in vivo potential. A structure-activity relationship study is also presented. Some of the test compounds were found to have in vivo efficacy towards the inhibition of PGD(2)-induced and OVA-induced vascular permeability in guinea pig conjunctiva.

Design, synthesis, and biological evaluation of new phosphodiesterase type 4 inhibitors.

The design, synthesis, and biological evaluation of new phosphodiesterase type 4 inhibitors, which possess new templates instead of a cyclohexane ring, are described. The mode of interaction with the enzyme is discussed based on the structure-activity relationship (SAR) data obtained for the synthesized inhibitors. Furthermore, the roles of three pharmacophores, a catechol moiety, a nitrile moiety, and acidic moieties, are discussed using in silico docking studies. More detailed biological evaluations of selected compounds are also presented.

Highly potent PDE4 inhibitors with therapeutic potential.

The hypothesis that the dose-limiting side effects of PDE4 inhibitors could be mediated via the central nervous system prompted us to design and synthesize a hydrophilic piperidine analog to improve the side effect profile of Ariflo 1, which is an orally active second-generation PDE4 inhibitor. During evaluation of various water-soluble piperidine analogs, 2a-b, 11b-14b, and 17a showed therapeutic potential in cross-species comparison studies. The following three findings were obtained: (1) The hydroxamic acid group, a well known metal chelator, caused a marked increase of inhibitory activity. (2) Water-soluble piperidine analogs lacked the configurational isomerism of Ariflo 1 without loss of inhibitory activity. (3) Replacement of the 4-methoxy residue with a difluoromethoxy residue led to an increase of in vivo potency. Structure-activity relationships are presented. Single-dose rat pharmacokinetic data for 11b, 12b, and 17a are also presented.

Clarification of mechanism of human sputum elastase inhibition by a new inhibitor, ONO-5046, using electrospray ionization mass spectrometry.

Liquid chromatography electrospray ionization mass spectrometry (LC/ESI-MS) to probe the nature of the covalent E-I complex was successfully applied to clarify the mechanism of human sputum elastase (HSE) inhibition by a new inhibitor, ONO-5046. The mass spectrum of the four HSE isozymes displayed their molecular ion peaks at m/z=26,018, 25,929, 25,200, and 25,054, respectively. Immediately after incubation, inactivation of HSE with ONO-5046 increased the four molecular ion peaks by approximately 84 amu, which was assigned to the mass unit of the pivaloyl moiety of ONO-5046. An additional minute of incubation of E-I complex restored the original molecular ion peaks. These observations strongly suggested that ONO-5046 inactivates HSE by a reversible 'acylation-deacylation' mechanism.

Regio- and stereoselective synthesis of (E)-alkene trans-Xaa-Pro dipeptide mimetics utilizing organocopper-mediated anti-S(N)2' reactions.

Proline dipeptides (Xaa-Pro) exist as an equilibrium mixture of cis- and trans-rotamers, which depends on the energy barriers for imide isomerization. This conformation mixture contributes to both structure and function of proline-containing peptides and proteins. Structural motifs resembling these cis- or trans-conformers have served as useful tools for elucidating contributions of proline residues in the physicochemical and biological profiles of structures which contain them. Among such motifs are alkene dipeptide isosteres which mimic cis- or trans-imide using (Z)- or (E)-alkene, respectively. In this report, the first regio- and stereoselective syntheses of (E)-alkene dipeptide isosteres (20, 31, and 35) corresponding to trans-proline dipeptides are described. Key to the synthesis of these mimetics is the anti-S(N)2' reaction of vinyl aziridines such as 15 or vinyl oxazolidinones such as 28 and 32 with organocopper reagents "RCu" (R = CH(2)SiMe(2)(Oi-Pr)). Reaction of cis-vinylaziridine 15 derived from L-serine with organocopper reagent gave a precursor of the trans-L-Ser-D-Pro type alkene isosteres 20, accompanied by an S(N)2 side product. One limitation with the use of such aziridine-mediated methodology is formation of the corresponding trans-aziridine 22, which leads to L-L type isosteres, that is unstable and obtainable only in low yield. On the other hand, both isomers of oxazolidinone derivatives can be easily obtained from N-Boc-protected amino alcohols. The reaction of trans- 28 or cis-oxazolidinone derivative 32 with organocopper reagents proceeds quantitatively with high regio- and diastereoselectivities in anti-S(N)2' fashion. Subsequent oxidative treatment of the newly introduced isopropoxydimethylsilylmethyl group yields trans-L-Ser-L-Pro 31 or trans-L-Ser-D-Pro type isosteres 35, respectively. Of note, synthesized isostere 31 can also be converted to trans-phosphoSer-Pro 42 and trans-Cys-Pro mimetics 44. The present synthetic methodology affords trans-Xaa-Pro alkene-type dipeptide isosteres in high yield with relatively simple manipulation.

Diastereoselective synthesis of new psi[(E)-CH=CMe]- and psi[(Z)-CH=CMe]-type alkene dipeptide isosteres by organocopper reagents and application to conformationally restricted cyclic RGD peptidomimetics.

Diastereoselective synthesis of new psi[(E)-CH=CMe]- and psi[(Z)-CH=CMe]-type alkene dipeptide isosteres corresponding to dipeptides having one N-methylamino acid, and application to bioactive peptides, are described. In a key reaction introducing the chiral alpha-alkyl group of the isosteres, organocopper-mediated alkylation of syn-beta-methylated gamma-mesyloxy-alpha,beta-enoate 26a afforded E- and Z-isomers of anti-S(N)2' products in a solvent-dependent manner. The resulting two isosteres, D-Phe-psi[(E)-CH=CMe]-L-Val 27a and D-Phe-psi[(Z)-CH=CMe]-L-Val 28b, which corresponded to trans- and cis-conformers of D-Phe-L-MeVal, respectively, were utilized in a structure-activity relationship study on cyclic RGD peptides 1 and 2, in company with a psi[(E)-CH=CH]-type alkene dipeptide isostere, D-Phe-psi[(E)-CH=CH]-L-Val. The cyclic isostere-containing pseudopeptides 3, 4, and 40 were synthesized and biological activity against integrin alpha(V)beta(3) and alpha(IIb)beta(3) receptors were also evaluated.

A practical synthesis and biological evaluation of 9-halogenated PGF analogues.

A series of 9-halo PGF analogues 1-2 and 5-13 were synthesized and biologically evaluated. Among the compounds, 2 was the best EP2-receptor agonist. A practical method of synthesizing 2 via the Julia olefination of an aldehyde 3 with an optically active sulfone 4, which was prepared by Sharpless asymmetric epoxidation of 15, was developed. Other 9-halogenated PGF analogues were synthesized essentially by the same procedure and evaluated. The absolute configuration of 16-OH of 2 was determined as S by the X-ray analysis of a salt consisting of a 1/1 molar ratio of 2 and L-lysine.

Diastereoselective synthesis of psi[(E)-CH=CMe]- and psi[(Z)-CH=CMe]-type dipeptide isosteres by organocopper-mediated anti-S(N)2' reaction.

[reaction: see text] Acyclic psi[(E)-CH=CMe]- and psi[(Z)-CH=CMe]-type dipeptide isosteres were efficiently synthesized. In a key reaction, alpha-alkylation of gamma-mesyloxy-beta-methyl-alpha,beta-unsaturated esters with organocyanocuprates in diethyl ether or tetrahydrofuran preferentially afforded the psi[(E)-CH=CMe]- or psi[(Z)-CH=CMe]-isomer, respectively, via anti-S(N)2' mechanism.

Diastereoselective synthesis of psi[(E)-CMe=CH]- and psi[(E)-CMe=CMe]- type dipeptide isosteres based on organocopper-mediated anti-S(N)2' reaction.

[reaction: see text] A straightforward synthetic route for the synthesis of diastereomerically pure psi[(E)-CMe=CH]- and psi[(E)-CMe=CMe]-type dipeptide isosteres was developed on the basis of regio- and stereoselective anti-S(N)2' alkylation of 3-(N-Boc-5-methyl-4-substituted-oxazolidin-2-on-5-yl)acrylates with organocopper reagents.