Inhibitors of human immunodeficiency virus type 1 protease containing 2-aminobenzyl-substituted 4-amino-3-hydroxy-5-phenylpentanoic acid: synthesis, activity, and oral bioavailability

Cloning and Expression of a Novel Leucine Dehydrogenase: Characterization and L-tert-Leucine Production

Among many genes encoding for amino acid dehydrogenase, a novel leucine dehydrogenase gene from Exiguobacterium sibiricum (EsiLeuDH) was isolated by using genome mining strategy. EsiLeuDH was overexpressed in Escherichia coli BL21 (DE3), followed by purification and characterization. The high thermostability of the enzyme confers its half-life up to 14.7 h at 50°C. Furthermore, the substrate specificity shows a broad spectrum, including many L-amino acids and aliphatic α-keto acids, especially some aryl α-keto acids. This enzyme coupled with recombinant formate dehydrogenase (FDH) was used to catalyze trimethylpyruvic acid (TMP) through reductive amination to generate enantiopure L-tert-leucine (L-Tle). In order to overcome the substrate inhibition effect, a fed-batch feeding strategy was adopted to transform up to 0.8 M of TMP to L-Tle, with an average conversion rate of 81% and L-Tle concentration of 65.6 g⋅L^–1. This study provides a highly efficient biocatalyst for the synthesis of L-Tle and lays the foundation for large-scale production and application of chiral non-natural amino acids.

Ring-construction/stereoselective functionalization cascade: total synthesis of pachastrissamine (jaspine B) through palladium-catalyzed bis-cyclization of propargyl chlorides and carbonates

Palladium(0)-catalyzed cyclization of bromoallenes, propargyl chlorides, and carbonates bearing hydroxy and benzamide groups as internal nucleophiles stereoselectively provides functionalized tetrahydrofuran. Cyclization reactivity is dependent on the relative configuration of the benzamide and leaving groups, and on the nature of the leaving groups. This bis-cyclization was used as the key step in a short total synthesis of pachastrissamine, which is a biologically active marine natural product.

Highly enantioselective alkynylation of aldehydes catalyzed by a new oxazolidine-titanium complex

The readily available and inexpensive new chiral oxazolidine in combination with Ti(O(i)Pr)(4) was found to catalyze the reaction of an alkynylzinc reagent with various types of aldehydes to generate chiral propargylic alcohols with high enantioselectivities (up to 95%) and excellent yields (up to 98%).

Structure-based optimisation of 2-aminobenzylstatine derivatives: potent and selective inhibitors of the chymotrypsin-like activity of the human 20S proteasome

We have identified 2-aminobenzylstatine derivatives that inhibit non-covalently the chymotrypsin-like activity of the human 20S proteasome. A structure-based optimisation approach has allowed us to improve the potency of this structural class of proteasome inhibitors from micromolar to nanomolar level. The new derivatives showed good selectivity against the trypsin-like and post-glutamyl-peptide hydrolytic activities of this enzyme.

A new structural class of selective and non-covalent inhibitors of the chymotrypsin-like activity of the 20S proteasome

We describe the identification and in vitro characterization of a series of 2-aminobenzylstatine derivatives that inhibit non-covalently the chymotrypsin-like activity of the 20S proteasome. Our initial SAR data demonstrate that the 2-aminobenzylstatine core structure can effectively serve as the basis for designing potent, selective and non-covalent inhibitors of the chymotrypsin-like activity of the 20S proteasome.

An Escherichia coli expression assay and screen for human immunodeficiency virus protease variants with decreased susceptibility to indinavir

We have developed a recombinant Escherichia coli screening system for the rapid detection and identification of amino acid substitutions in the human immunodeficiency virus (HIV) protease associated with decreased susceptibility to the protease inhibitor indinavir (MK-639; Merck & Co.). The assay depends upon the correct processing of a segment of the HIV-1 HXB2 gag-pol polyprotein followed by detection of HIV reverse transcriptase activity by a highly sensitive, colorimetric enzyme-linked immunosorbent assay. The highly sensitive system detects the contributions of single substitutions such as I84V, L90M, and L63P. The combination of single substitutions further decreases the sensitivity to indinavir. We constructed a library of HIV protease variant genes containing dispersed mutations and, using the E. coli recombinant system, screened for mutants with decreased indinavir sensitivity. The discovered HIV protease variants contain amino acid substitutions commonly associated with indinavir resistance in clinical isolates, including the substitutions L90M, L63P, I64V, V82A, L24I, and I54T. One substitution, W6R, is also frequently found by the screen and has not been reported elsewhere. Of a total of 12,000 isolates that were screened, 12 protease variants with decreased sensitivity to indinavir were found. The L63P substitution, which is also associated with indinavir resistance, increases the stability of the isolated protease relative to that of the native HXB2 protease. The rapidity, sensitivity, and accuracy of this screen also make it useful for screening for novel inhibitors. We have found the approach described here to be useful for the detection of amino acid substitutions in HIV protease that have been associated with drug resistance as well as for the screening of novel compounds for inhibitory activity.

cis-1-Aminoindan-2-ol in Asymmetric Syntheses

A review on cis-1-aminoindan-2-ol derived asymmetric syntheses is described.

Time-resolved fluorescence anisotropy of HIV-1 protease inhibitor complexes correlates with inhibitory activity

The tryptophan time-resolved fluorescence intensity and anisotropy of the HIV-1 protease dimer is shown to be a quick and efficient method for the conformational characterization of protease inhibitor complexes. Four fluorescence lifetimes were needed to adequately describe the fluorescence decay of the two tryptophan residues, W6 and W42, per protease monomer. As a result of the wavelength dependence of the respective amplitudes, the 2.06 ns and the 4.46 ns decay constants were suggested to be the intrinsic fluorescence lifetimes of the more solvent-exposed W6 and the less exposed W42 residues, respectively. Analysis of the fluorescence anisotropy decay yielded a short correlation time of 250 ps corresponding to local chromophore motions, and a long correlation time of 12.96 ns resulting from overall rotation of the protease enzyme. Fluorescence lifetimes and rotational correlation times changed when inhibitors of the HIV-1 protease were added. The effects of 11 different inhibitors including statine-derived, hydroxyethylamine-derived, and 2 symmetrical inhibitors on the protease fluorescence dynamics were investigated. Inhibitor binding is shown to induce an increase of the mean fluorescence lifetime taumean, an increase of the short rotational correlation time phi1, as well as a decrease of the long rotational correlation time phi2. The mean rotational correlation time phimean was identified as the global dynamic parameter for a given molecular complex, which correlates with the inhibitor dissociation constant Ki, and therefore with the activity of the inhibitor.

A Convenient Enzymatic Route to Optically Active l-Aminoindan-2-ol: Versatile Ligands for HIV-1 Protease Inhibitors and Asymmetric Syntheses

(1S,2R)- and (1R,2S)-l-aminoindan-2-ol were prepared in high enantiomeric excess (>96%) by an immobilized lipase-catalyzed selective acylation of racemic trans- l-azidoindan-2-ol.

Paracyclophanes: a novel class of water-soluble inhibitors of HIV proteinase

A versatile synthesis of functionalized para- and metacyclophanes (macrocycles with one or more aromatic rings incorporated; ansa-compounds) has been developed. Cyclophanes constitute a novel building block for potent human immunodeficiency virus (HIV) protease inhibitors. The synthesis of the macrocyclic ring system was achieved by regio- and stereospecific ring opening of N-protected 4-amino-2,3-epoxy-5-phenylpentanoates with appropriate alpha, omega-diamines and consecutive ring closure under high dilution conditions. The resulting macrocyclic building blocks enabled further broad and flexible derivation. Paracyclophanes, containing oxyethylene substructures, were found to dissolve in phosphate-buffered saline at concentrations as high as 3 mg/mL at physiological pH. Several derivatives with Ki values lower than 10 nM and antiviral activities in the range of 15-50 nM have been obtained. The influence of the ring size and of the substitution pattern of the cyclophane moiety on enzyme inhibition, antiviral activity, and water solubility are discussed. Preliminary data on oral bioavailability in mice are given for selected compounds.