Norton P. Peet

Peptide aldehydes as inhibitors of HIV protease

We have recently shown that α‐MAPI, a peptidic aldehyde of microbial origin, inhibits the HIV protease with a potency comparable to pepstatin, having, differently from pepstatin, no activity on other aspartic proteases. In this study different peptide derivatives containing a C‐terminal aldehyde have been tested to assess the potential of this function for the inhibition of HIV protease. The results of our analysis correspond with the recently published subsite preferences of the viral enzyme, indicating that aldehydes bind to the active site of the HIV protease. Our data suggest that peptide aldehydes can act in their hydrated forms as transition state analogues with the most potent inhibitor having an IC50 of 0.9 μM.

Pyrrolidine and hexahydro-1 H-azepine mimics of the ‘flap up’ mannosyl cation

Abstract The pyrrolidine 4, 6-amino-1,4,6-trideoxy-1,4-imino–D-mannitol dihydrochloride, and the hexahydro-1 H–azepine 5, 4-amino-1,4,6-trideoxy-1,6-imino-D-mannitol dihydrochloride, were synthesized as potential inhibitors of α-mannosidase.

Oxidation of α-hydroxy esters to α-keto esters using the dess-martin periodinane reagent

Abstract The oxidation of α-hydroxy esters, including peptidyl α-hydroxy esters, with the Dess-Martin periodinane reagent is a useful and general method for the preparation of α-keto esters.

Synthesis of a peptidyl 2,2-difluoro-3-aminopropionate

Abstract Ethyl 3-(benzylamino)-2,2-difluoro-4-methylpentanoate (4) was prepared via a Reformatsky reaction of ethyl bromodifluoroacetate with the imine from isovaleraldehyde and benzylamine. N-Debenzylation of 4 gave amino ester 6, which was coupled to Boc·Ala·Ala·Pro·OH to provide a potential proteinase inhibitor.

Time-dependent inactivation of steroid C17(20) lyase by 17β-cyclopropyl ether-substituted steroids

Abstract Androstenes bearing a cyclopropyl group attached to the C-17β position with a heteroatom linker, designed as mechanism-based inhibitors of steroid C 17(20) lyase, were found to be potent, time-dependent inhibitors of this enzyme.

Biological characterization of A-ring steroids.

Hydroxylated 2,19-methylene-bridged androstenediones were designed as potential mimics of enzyme oxidized intermediates of androstenedione. These compounds exhibited competitive inhibition with low micromolar affinities for aromatase. These inhibitory constants (Ki values) were 10 times greater than the 2,19-methylene-bridged androstenedione constant (Ki = 35-70 nM). However, expansion of the 2,19-carbon bridge to ethylene increased aromatase affinity by 10-fold (Ki = 2 nM). Substitution of a methylene group with oxygen and sulfur in this expanded bridge resulted in Ki values of 7 and 20 nM, respectively. When the substituent was an NH group, the apparent inhibitory kinetics changed from competitive to uncompetitive. All of these analogs exhibited time-dependent inhibition of aromatase activity following preincubation of the inhibitor with human placental microsomes prior to measuring residual enzyme activity. Part of this inhibition was NADPH cofactor-dependent for the 2,19-methyleneoxy- but not for the 2,19-ethylene-bridged androstenedione. The time-dependent inhibition for these four analogs was very rapid since they exhibited tau 50 values, the t1/2 for enzyme inhibition at infinite inhibitor concentration, of 1 to 3 min. These A-ring-bridged androstenedione analogs represent a novel series of potent steroidal aromatase inhibitors. The restrained A-ring bridge containing CH2, O, S, or NH could effectively coordinate with the heme of the P450 aromatase to allow the tight-binding affinities reflected by their nanomolar Ki values.

A-ring bridged steroids as potent inhibitors of aromatase

The design and syntheses of androstenedione derivatives with bridges spanning the 2,19-, 3,19-, 4,19- and 6, 19-positions are described. 2,19-Bridged compounds bearing hydroxyl groups on the two-carbon bridge (3a and 3b) were designed as stable carbon analogs of potential lactol intermediates in the enzymatic conversion of androgens to estrogens. Compounds 3a and 3b are competitive inhibitors of aromatase. Pyran 25 is a potent, time-dependent inhibitor of aromatase with partial NADPH dependence. These data suggest a mechanism of inhibition for 25 which involves both tight-binding competitive and mechanism-based components, with the former predominating. The sulfur, amino, and all carbon analogs of pyran 25 were prepared. Thiopyran 36, piperidine 42 and the all-carbon analog 47 are also time-dependent inhibitors of aromatase. Compound 47 is the most potent inhibitor and its time-dependent inhibition is not NADPH dependent. The kinetics of piperidine 42 suggest uncompetitive inhibition.

Synthesis and antibacterial evaluation of new, unsymmetrical triaryl bisamidine compounds

Herein we describe the synthesis and antibacterial evaluation of a new, unsymmetrical triaryl bisamidine compound series, [Am]-[indole]-[linker]-[HetAr/Ar]-[Am], in which [Am] is an amidine or amino group, [linker] is a benzene, thiophene or pyridine ring, and [HetAr/Ar] is a benzimidazole, imidazopyridine, benzofuran, benzothiophene, pyrimidine or benzene ring. When the [HetAr/Ar] unit is a 5,6-bicyclic heterocycle, it is oriented such that the 5-membered ring portion is connected to the [linker] unit and the 6-membered ring portion is connected to the [Am] unit. Among the 34 compounds in this series, compounds with benzofuran as the [HetAr/Ar] unit showed the highest potencies. Introduction of a fluorine atom or a methyl group to the triaryl core led to the more potent analogs. Bisamidines are more active toward bacteria while the monoamidines are more active toward mammalian cells (as indicated by low CC50 values). Importantly, we identified compound P12a (MBX 1887) with a relatively narrow spectrum against bacteria and a very high CC50 value. Compound P12a has been scaled up and is currently undergoing further evaluations for therapeutic applications.

Pyrazoloquinazolines from 2-aminobenzoylhydrazine

Brief treatment of 2-aminobenzoylhydrazine (2) with diethyl acetonedicarboxylate in ethanol gave 3-(benzoylhydrazono)-pentanedioic acid diethyl ester (3). However, with extended reaction times the product of this condensation was 3-amino-3,4-dihydro-4-oxo-2,2(1H)-quinazolinediacetate (5). In the latter transformation, diethyl 1,3,4,5-tetrahydro-5-oxo-2H-1,3,4-benzotriazepine-2,2-diacetate (6) is an obligatory intermediate. Cyclization of 5 with sodium carbonate in ethanol gave ethyl 2,3,4,9-tetrahydro-2,9-dioxopyrazolo[5,1-b]quinazoline-3a(1H)-acetate (8), and methylation of 8 afforded its 1-methyl derivative (9)

Janus compounds: dual inhibitors of proteinases

Abstract The concept of dual proteinase inhibition has been demonstrated with the preparation of unsymmetrical bis-terephthalamides.