Yoshihisa Kobayashi

Toward Creation of a Universal NMR Database for Stereochemical Assignment: The Case of 1,3,5-Trisubstituted Acyclic Systems

Using the diastereoisomeric triols 1a – d (Fig. 1) and examples summarized in Fig. 2, the central C-atom of acyclic 1,3,5-triols is demonstrated to exhibit a distinctive chemical shift that is dependent on the 1,3- and 3,5-relative configuration, but is independent of the functionalities present outside of this structural motif. These NMR characteristics are then used to predict the relative configuration of several natural products (Fig. 7). In addition, an example is given to show the possibility of assembling an NMR database for a larger array of functional groups from NMR databases of smaller arrays of functional groups.

Facile Procedure for Generating Side Chain Functionalized Poly(α-hydroxy acid) Copolymers from Aldehydes via a Versatile Passerini-Type Condensation

A general method for synthesizing alpha-hydroxy N-acylindoles in one-pot via an acid-catalyzed condensation of a convertible isonitrile with water and various aldehydes is presented. These intermediates were incorporated into poly(alpha-hydroxy acid) copolymers bearing residues with functionalizable side chains, which could be further modified through Cu(I)-catalyzed azide-alkyne cylcoaddition reactions. This versatile synthetic strategy provides access to side chain functionalized poly(alpha-hydroxy acid) copolymers from readily available aldehydes, making it potentially useful as an approach to synthesize biodegradable polymers with new, tunable properties.

Total synthesis of (+/-)-dysibetaine.

The marine natural product dysibetaine was synthesized in racemic form from a levulinic acid derivative using a convertible isocyanide and an ammonium acetate in the Ugi 4-center-3-component condensation reaction.

2-Nitrophenyl Isocyanide as a Versatile Convertible Isocyanide : Rapid Access to a Fused γ-Lactam β-Lactone Bicycle

2-Nitrophenyl isocyanide is introduced as a convertible isocyanide with demonstration of its feasibility and applicability in an efficient synthesis of the fused gamma-lactam beta-lactone bicycle of proteasome inhibitor omuralide. Starting from a linear keto acid precursor, the fused gamma-lactam beta-lactone bicycle was prepared in four steps by a sequential biscyclization strategy; a stereocontrolled Ugi reaction and the concomitant direct beta-lactonization following the formation of an N-acylbenzotriazole intermediate. The N-acylbenzotriazole is amenable to intra- or intermolecular attack from a variety of nucleophiles with a catalytic amount of base to form the pyroglutamic acid derivatives.

Identification of novel deoxyribofuranosyl indole antimicrobial agents

Three novel deoxyribofuranosyl indole derivatives, FG050227 (1), FG050223 (2) and FG050204 (3), were identified as antimicrobial agents effective against Gram-positive bacterial strains and some fungi. The MIC values of (1), (2) and (3) against methicillin-resistant Staphylococcus aureus were 3.0, 6.0 and 13 μg ml−1, respectively. Compounds 1 and 3 had bactericidal activity against exponentially growing S. aureus and inhibited biosynthesis of peptidoglycan, protein, RNA and DNA. Compound 2 was bacteriostatic and inhibited the biosynthesis of protein and RNA. The results indicated that deoxyribofuranosyl indole derivatives could be potential lead compounds for the development of antimicrobial agents.

Synthesis of the Common Propellane Core Structure of the Hasubanan Alkaloids

The racemic synthesis of the common propellane core structure found in various hasubanan alkaloids is reported. The successful completion hinged upon the stereocontrolled construction of the cis-substituted heterobicycle as a precursor for the intramolecular Dieckmann condensation. A novel strategy is introduced for the facile hydrolysis of a sterically demanding carboxamide under a mild condition. The 2-nitroanilide obtained by the Goldberg arylation of a carboxamide with 2-iodonitrobenzene was readily converted to the corresponding ester derivative by way of N-acylbenzotriazole. We expect that the reported synthetic route will allow the synthesis of a series of hasubanan alkaloids starting from the correspondingly functionalized 2-tetralone derivatives.

Scalable preparation of both enantiomers of 2-(1-hydroxy-2-oxocyclohexyl)acetic acid.

The efficient, scalable preparation of both enantiomers of 2-(1-hydroxy-2-oxocyclohexyl)acetic acid in enantiomerically pure form is reported using environmentally benign conditions in 30% overall yield (6 steps) for the (S)-isomer, in 27% (7 steps) for the (R)-isomer, from cyclohexanone.