Tatsuo Ohtsuka

Design and synthesis of novel benzofurans as a new class of antifungal agents targeting fungal N-myristoyltransferase. Part 1

Potent and selective Candida albicans N-myristoyltransferase (CaNmt) inhibitors have been identified through optimization of a lead compound 1 discovered by random screening. The inhibitor design is based on the crystal structure of the CaNmt complex with compound (S)-3 and structure-activity relationships (SARs) have been clarified. Modification of the C-4 side chain of 1 has led to the discovery of a potent and selective CaNmt inhibitor 11 (RO-09-4609), which exhibits antifungal activity against C. albicans in vitro.

Synthesis and biological activities of benzofuran antifungal agents targeting fungal N-myristoyltransferase

The C-4 side chain modification of lead compound 1 has resulted in the identification of a potent and selective Candida albicans N-myristoyltransferase (CaNmt) inhibitor RO-09-4609, which exhibits antifungal activity against C. albicans in vitro. Further modification of its C-2 substituent has led to the discovery of RO-09-4879, which exhibits antifungal activity in vivo. The drug design is based on X-ray crystal analysis of a CaNmt complex with benzofuran derivative 4a. The optimization incorporates various biological investigations including a quasi in vivo assay and pharmacokinetic study. The computer aided drug design, synthesis, structure-activity relationships, and biological properties of RO-09-4879 are described in detail.

Crystal Structures of Candida albicans N-Myristoyltransferase with Two Distinct Inhibitors

Myristoyl-CoA:protein N-myristoyltransferase (Nmt) is a monomeric enzyme that catalyzes the transfer of the fatty acid myristate from myristoyl-CoA to the N-terminal glycine residue of a variety of eukaryotic and viral proteins. Genetic and biochemical studies have established that Nmt is an attractive target for antifungal drugs. We present here crystal structures of C. albicans Nmt complexed with two classes of inhibitor competitive for peptide substrates. One is a peptidic inhibitor designed from the peptide substrate; the other is a nonpeptidic inhibitor having a benzofuran core. Both inhibitors are bound into the same binding groove, generated by some structural rearrangements of the enzyme, with the peptidic inhibitor showing a substrate-like binding mode and the nonpeptidic inhibitor binding differently. Further, site-directed mutagenesis for C. albicans Nmt has been utilized in order to define explicitly which amino acids are critical for inhibitor binding. The results suggest that the enzyme has some degree of flexibility for substrate binding and provide valuable information for inhibitor design.

Structure of cyclothiazomycin, a unique polythiazole-containing peptide with renin inhibitory activity. Part 2. Total structure

Abstract Structure of cyclothiazomycin, a novel renin inhibitor isolated from cultured broth of Streptomyces sp . NR0516, was determined to be a unique polythiazole-containing peptide related to thiostrepton and noshiheptide. Its structure including stereochemistry was established based on NOESY experiments.

Structure of cyclothiazomycin, a unique polythiazole-containing peptide with renin inhibitory activity. Part 1. Chemistry and partial structures of cyclothiazomycin

Cyclothiazomycin is a novel renin inhibitor produced by Streptomyces sp.NR0516 (IC50 1.66μM). Its molecular formula was determined to be C59H64H18O14S7 (MW .1472) based on high-resolution FAB mass and NMR spectroscopy. Five fragments of cyclothiazomycin containing thiazole, thiazoline, heterocyclic chromophore were clarified by extensive 2D-NMR experiments.

Cassette dosing approach and quantitative structure-pharmacokinetic relationship study of antifungal N-myristoyltransferase inhibitors.

Pharmacokinetic (PK) parameters of N-myristoyltransferase (Nmt) inhibitors were measured, and a multivariate quantitative structure-pharmacokinetic relationship (QSPKR) model for predicting rat elimination half-life (t(1/2)) values was constructed. One hundred seven benzofuran derivatives have been selected as the data set for QSPKR analysis. The correlation between the t(1/2) values and 30 physicochemical descriptors was examined by a stepwise multiple linear regression method. The statistical analysis gives a significant QSPKR model (r = 0.843) with the following three variables: partial negative surface area (PNSA), atomic-based octanol/water partition coefficient (AlogP), and the number of rotational bonds (Rotlbonds). The QSPKR model obtained is predictive and simple, and would give a direction for designing new Nmt inhibitors having good PK profiles.

3D-QSAR study of antifungal N-myristoyltransferase inhibitors by comparative molecular surface analysis

Abstract The correlation between the molecular electrostatic potential (MEP) on benzofuran inhibitors and the N-myristoyltransferase (Nmt) inhibitory activity is investigated by a three-dimensional quantitative structure–activity relationship (3D-QSAR) approach. To each compound, a Kohonen neural network (KNN) is used to project the MEP values on a Connolly surface into a two-dimensional map. Each node in the KNN map is coded by the associated MEP value of the occupying sampling point and all the coding nodes are collected together to define chemical descriptors. The best partial least squares (PLS) model with the selected descriptors is searched among the possible candidate models by genetic algorithm (GA). The resulting best model is significantly more predictive than the one with all chemical descriptors. The model has given additional information about the binding of a benzofuran inhibitor to Nmt.

Structural elucidation of arthrobacilins A, B and C, structurally unique secondary metabolites of A microorganism

Abstract Arthrobacilins are novel cell growth inhibitors produced by Arthrobactor sp. NR2967. Their structures have been elucidated based on various NMR experiments and acid hydrolysis.