In a simple, one-pot, catalyst-free procedure starting from heterocyclic nitroenamines, substituted anilines and ethyl glyoxylate new ethyl 2-arylamino-3-nitro-propionates were prepared in good to ...excellent yields. Depending on the substituent pattern of the anilines applied, two routes for the one-pot reaction are suggested. Additionally, it was demonstrated that these multifunctional compounds of aza-Morita–Baylis–Hillman type were also formed in two-step protocols either from imines and nitroenamines or from the adducts of nitroenamines and ethyl glyoxylate with anilines.
Display omitted
As part of our ongoing investigation into the synthetic application of nitroenamines several new densely substituted pyrimidine and pyrrolo-pyrimidine derivatives were prepared. Thus, ...2-nitromethylenepyrrolidine and some open chain nitroenamines of phenyl-(2-nitro-1-phenyl-vinyl)-amine type were reacted with ethyl glyoxylate and a substituted aniline usually in a one-pot procedure to furnish the key intermediates for a subsequent cyclization. These compounds including a molecular fragment of 1,3-diamine type were subjected to a simple ring closure with formaldehyde to give the title compounds in good yields. The protocol reported has the advantages of mild reaction conditions, easy workup and inexpensive reagents.
In an attempted removal of the 4-methoxy-phenyl protecting group from the 4-methoxy-phenyl substituted hexahydropyrrolo1,2-cpyrimidine derivative, an unexpected periodic acid mediated ring cleavage and phenyl group migration was discovered. The structures of the synthesized new compounds were confirmed by spectral data, and, particularly, the hindered rotation and the unusual 1H NMR characteristics of 4-(4-nitro-phenyl)-but-3-enoic acid ethyl ester derivative were discussed.
Display omitted
The structure of a complex between a peptide inhibitor with the sequence N-acetyl-Thr-Ile-Nle-ψCH$_{2}$-NH-Nle-Gln-Arg.amide (Nle, norleucine) with chemically synthesized HIV-1 (human ...immunodeficiency virus 1) protease was determined at 2.3 Å resolution (R factor of 0.176). Despite the symmetric nature of the unliganded enzyme, the asymmetric inhibitor lies in a single orientation and makes extensive interactions at the interface between the two subunits of the homodimeric protein. Compared with the unliganded enzyme, the protein molecule underwent substantial changes, particularly in an extended region corresponding to the ``flaps'' (residues 35 to 57 in each chain), where backbone movements as large as 7 Å are observed.
A fluorescence polarization assay was designed to measure proteolytic cleavage of a specific peptide substrate for human cytomegalovirus protease. The peptide substrate was derivatized by ...biotinylation of a γ-aminobutyric acid-modified amino-terminus and labeled with 5-(4,6-dichlorotriazinyl)aminofluorescein at the carboxy-terminus. Incubation of this substrate with recombinant human cytomegalovirus protease and subsequent addition of egg white avidin produced a polarization signal that was proportional to the relative amounts of cleaved and uncleaved substrate. The uncleaved substrate produced a high polarization value upon binding to avidin, whereas the cleaved, low-molecular-weight fluorescently tagged peptide that cannot bind to avidin produced a low polarization value. The inhibitory activity of a 3,4-dichloroisocoumarin against the protease was evaluated by comparing the change in polarization with a noninhibited control. The fluorescence polarization protease assay does not suffer from interference due to the presence of absorptive interferants making this a convenient, homogenous assay for high throughput screening.
A series of analogues of 2-iminopiperidine have been prepared and shown to be potent inhibitors of the human nitric oxide synthase (NOS) isoforms. Methyl substitutions on the 4-position (3) or 4- and ...6-positions (8) afforded the most potent analogues. These compounds exibited IC50 values of 0.1 and 0.08 μM, respectively, for hiNOS inhibition. Substitution with cyclohexylmethyl at the 6-position (13) afforded an inhibitor that showed the best selectivity for hiNOS versus heNOS (heNOS IC50/hiNOS IC50 = 64). Following oral administration, inhibitors were found to decrease serum nitrite/nitrate levels in an in vivo rat endotoxin assay. This series of 2-iminopiperidines were prepared via the described synthetic methodologies. The effect of ring substitutions on potency and selectivity for this class of cyclic amidines as NOS inhibitors is described.
The potency and selectivity of a series of 5-hetero-2-iminohexahydroazepines were examined as inhibitors of the three human NOS isoforms. The effect of ring substitution of the 5-carbon for a ...heteroatom is presented. Potencies (IC
50's) for these inhibitors are in the low micromolar range for hi-NOS with some examples exhibiting a 500× selectivity versus hec-NOS.
The potency and selectivity of a series of 5-hetero-2-iminohexahydroazepines were examined as selective inhibitors human i-NOS. The effect of ring substitution of the 5-carbon for a hetero atom is presented. Potencies (IC
50's) for these inhibitors are in the low micromolar range for hi-NOS with some examples exhibiting a 500×selectivity versus hec-NOS.
Novel fluorogenic substrates for human immunodeficiency viral protease have been developed based on the principle of fluorescence energy transfer. Starting from a p24/p15 cleavage site-derived ...hexapeptide substrate. Ac-Thr-Ile-Nle-Nle-Gln-Arg-NH2, incorporation of 2-aminobenzoic acid in place of the acetyl group as the donor and p-NO2-Phe at the P1' position as acceptor gave the intramolecularly quenched fluorogenic substrate. Cleavage of the substrate by HIV protease released the fluorescent N-terminal tripeptide from its close apposition to the quenching nitrobenzyl group, resulting in enhanced fluorescence. An automated assay based on 96-well microtiter plates and a fluorometric plate reader have been developed, which allow high throughput of compounds in the search for HIV protease inhibitors.
