Hiromu Harada

Upregulation of Retinal Vascular Endothelial Growth Factor mRNAs in Spontaneously Diabetic Rats without Ophthalmoscopic Retinopathy

Vascular endothelial growth factor (VEGF) has recently been shown to be involved in the pathogenesis of proliferative diabetic retinopathy. However, its involvement in the development of the early phase of diabetic retinopathy is not fully understood. In this study we investigated the retinal VEGF mRNA level in spontaneously diabetic Otsuka Long-Evans Tokushima fatty (OLETF) rats, a model of non-insulin-dependent diabetes, without overt retinopathy, using quantitative reverse-transcription polymerase chain reaction. The retinal VEGF mRNA level was 2.2 times higher (p < 0.0005) in OLETF rats than in control rats at the age of 60 weeks. Moreover, their retinal mRNA level was positively correlated with serum concentration of advanced glycation end products (AGEs) but not to serum glucose concentration. Furthermore, the peak latency of the oscillatory potentials in the electroretinogram, one of the most sensitive markers for the early phase of diabetic retinopathy, was significantly prolonged in OLETF rats (p < 0.05), being also correlated with the serum AGE concentration. The results thus suggest that AGEs, which are formed acceleratedly in diabetic conditions, are involved in the development of the early phase of diabetic retinopathy probably through the induction of retinal VEGF mRNAs.

A stereoselective synthesis of cyclohexylnorstatine, the key component of a renin inhibitor

Abstract The title synthesis could be accomplished by employing the novel addition reaction of a Grignard reagent with an imine in the presence of cerium(III) chloride.

A stereoselective synthesis of the (2R, 3S)- and (2S, 3R)-3-amino-2-hydroxybutyric acid derivatives, the key components of a renin inhibitor and bestatin.

Abstract The title synthesis was achieved by featuring the [2+2]-cycloaddition reaction of benzyloxyketene with a chiral imine derived from methyl (R)- or (S)-mandelate, alcoholysis of the formed 3,4-cis disubstituted β-lactam under acidic conditions, and reductive removal obtained by the [2+2]-cycloaddition reaction employing achiral and chiral imines derived from benzylamine, p-anisidine, di-panisylmethylamine, and (S)-l-phenylethylamine were also reported. Stereoselectivity of the [2+2]-cycloaddition reaction could be explained by the initial formation of a zwitter-ionic intermediate and its subsequent conrotatory ring closure.

An efficient synthesis of methyl N-[2-(R)-(1-napthylmethyl)-3-(morpholinocarbonyl)propionyl]-(S)-histidinate, the key synthetic intermediate of renin inhibitors

Optically pure (R)-(1-naphthylmethyl)succinic acid could be efficiently prepared by a combination of optical resolution and racemization of the undesired enantiomer or by catalytic asymmetric reduction of (1-naphthylmethylene)succinic acid over a rhodium (I)-chiral phosphine complex. Highly chemoselective amide formation of di-4-nitrophenyl (R)-(1-naphthylmethyl)succinate with morpholine followed by coupling with methyl (S)-histidinate readily produced the title key synthetic intermediate.

A Novel Synthesis of Cyclohexylnorstatine Isopropyl Ester, the C-Terminal Component of a Renin Inhibitor

The title compound was produced diastereoselectively in racemic and optically active forms by employing the [2+2] cycloaddition reaction of an imine with benzyloxyketene followed by acidic alcoholysis of the formed 3,4-cis-disubstituted β-lactam with isopropanol

Conformational study of a potent human renin inhibitor: X-ray crystal structure of isopropyl (2R,3S)-4-cyclohexyl-2-hydroxy-3-{N-[(2R)-2-morpholinocarbonylmethyl-3-(1-naphthyl)propionyl]-L-histidylamino}butyrate (KRI-1314), a pentapeptide analogue with amino acid sequence corresponding to the cleavage site of angiotensinogen

A potent inhibitor of renin, isopropyl (2R,3S)-4-cyclohexyl-2-hydroxy-3-{N-[(2R)-2-morpholino-carbonylmethyl-3-(1-naphthyl)propionyl]-L-histidylamino}butyrate (KRI-1314), was crystallized as a cinnamic acid salt. The crystal structure of KRI-1314 was determined by X-ray analysis, and the conformation is discussed in relation to the inhibitory activity. The backbone chain of the molecule was largely twisted at the unusual amino acid residue of cyclohexylnorstatine. The observed conformation was compared with that of the model pentapeptide corresponding to the scissile site of angiotensinogen. The stacking interaction was formed between the histidine side-chains related by the crystallographic 2-fold screw axis. The histidine imidazole rings were further fixed by hydrogen bonds with the cinnamic acid. The water molecule of crystallization mediated the hydrogen-bonding bridge of the cinnamic acid with the hydroxy oxygen of the cyclohexylnorstatine. Such interactions appear to be very important in considerations of inhibitor-or substrate-binding mechanisms against renin.

Design and synthesis of an orally potent human renin inhibitor containing a novel amino acid, cyclohexylnorstatine

An orally potent human renin inhibitor (1a) containing a novel amino acid, (2R,3S)-3-amino-4-cyclohexyl-2-hydroxybutyric acid named cyclohexylnorstatine, has been designed from the angiotensinogen transition-state and synthesized.

A practical synthesis of an orally potent renin inhibitor, isopropyl (2R,3S)-4-cyclohexyl-2-hydroxy-3-{N-[(2R)-2-morpholinocarbonylmethyl-3-(1-naphthyl)propionyl]-L-histidyl}aminobutyrate

The practical synthesis of an orally potent human renin inhibitor, isopropyl (2R,3S)-4-cyclohexyl-2-hydroxy-3-{N-[(2R)-2-morpholinocarbonylmethyl-3-(1-naphthyl)propionyl]-L-histidyl}-aminobutyrate, is presented. Optically pure cyclohexylnorstatine isopropyl ester (P1–P1′ moiety) was diastereoselectively and simply prepared from L-phenylalanine methyl ester. In a one-pot reaction, N-[(2R)-2-morpholinocarbonylmethyl-3-(1-naphthyl)propionyl]-L-histidine methyl ester (P4–P2moiety) was conveniently hydrolysed, protected with a Boc group attached to the side-chain imidazole function, and coupled with the cyclohexylnorstatine ester to give the optically pure target renin inhibitor.