Yoshifumi Yuasa

One-step synthesis of 4-aminodihydrobenzofurans and 4-hydroxyindoles via dehydrogenation-heteromercuration of 2-alyl-3-aminocyclohexenones using mercury(II) acetate

Abstract On treatment of the 2-allyl-3-aminocyclohexenones with mercury(II) acetate, either sequence, dehydrogenation—oxymercuration or dehydrogenation—aminomercuration, occurred depending on the nature of the amino group in the substrate to yield the dihydrobenzofurans or indoles, respectively.

Resolution of Racemic Rhododendrol by Lipase-Catalyzed Enantioselective Acetylation

Abstract Both (R)- and (S)-enantiomers of rhododendrol were prepared in high enantiomeric exess by lipase from Pseudomonas cepacia (Amano PS)-catalyzed acetylation of racemic 1 with vinyl acetate at room temperature. Especially, in the case of using acetonitrile as the solvent, by-products 4 and 5 were minimized.

An improved synthesis of (S)-aspartyl-(7,7-dimethylnorborn-2R-yl)-(S)-alanine methyl ester, a new high intensity artificial sweetener

Abstract (S)-Aspartyl-(7,7-dimenthylnorborn-2R-yl)-(S)-alanine methyl ester ( 1 ) was synthesized in nine steps from (+)-α-fenchyl alcohol ( 3 ) as a chiral synthon. Crucial steps for controlling the side-chain stereochemistry of 1 , required for the manifestation of sweetness, were the catalytic hydroformylation of the olefin 4 and the enzymatic resolution of the racemic amino acid 9 using acylase I.

The sweetness and stereochemistry of l-aspartyl-fenchylaminoalcohol derivatives

Abstract Four fenchylaminoalcohols were derived from ( + )-fenchone in five steps. They were resolved with ( + )- and (−)-tartaric acid, then condensed with N-carbobenzoxy-L-aspartic acid β-benzylester followed by hydrogenolysis to give four L-aspartyl-fenchylaminoalcohols. By the evalution of their taste, only (2R,3R)-aminoalcohol showed potent sweetness.

Stereoselective Synthesis of (2E, 6E, 10E)‐ Geranylgeraniol from Geranyllinalyl Acetate via Palladium‐Catalyzed Amination

Abstract Amination of geranyllinalyl acetate 1 with diethylamine and Pd(OAc)2 · 2PPh3 as catalyst gave N,N‐diethylgeranylgeranylamine 3 (E/Z=91/9) in 85% yield. Amine 3 was treated by ethyl chloroformate followed by KOAc to give geranylgeranyl acetate 2 in 82% yield. Then 2 was hydrolyzed to afford geranylgeraniol 4 in 94% yield.

The Oxidation of 3-Aryl-1-propenes by Oxidative System of RuCl3-NaIO4-Phase Transfer Catalyst

Abstract Methyleugenol 1a was oxidized to give 3,4-dimethoxyphenylacet-aldehyde by the oxidative system containing the RuCl3-NaIO4-phase transfer catalyst. The yield and spectroscopic properties were obtained from the stable acetaldoxim 3a. Furthermore, this oxidation system could be applied to other arylpropenes, thus, safrole, 4-methoxyallylbenzene, allylbenzene, and the corresponding arylacetaldehyde formed.

A Facile Synthesis of (2R 3S)-1-Amino-3-tert-butoxycarbonylamino-2-hydroxy-4-phenylbutane;A Useful Component Block of HIV Protease Inhibitor

Abstract (S)-3-tert-Butoxycarbonylamino-1-nitro-2-oxo-4-phenylbutan 4 was converted to (2R, 3S)-1-amino-3-tert-butoxycarbonylamino-2-hydroxy-4-phenylbutane 5a by a catalytic hydrogenation, or NaBH4-TiCl4 reduction followed by hydrogenation in favorable diastereoselectivity, a component of the HIV protease inhibitor VX-478.

A Convenient Synthesis of α-Fenchol from trans-2-Pinanol Using a Solid Acid Catalyst

ABSTRACT trans-2-Pinanol was directly rearranged to give α-fenchol in good yield by heating with aluminum phosphate as a solid acid catalyst.

Palladium(II) complexation of ambidentate cis-s-cis-enaminones: synthesis of some bis(4-anilinopent-3-en-2-onato)- and bis(3-amino-1-phenylbut-2-en-1-onato)-complexes of palladium(II) and X-ray crystal structure of bis[4-(2-bromoanilino)pent-3-en-2-onato]palladium(II)

Condensation of acetylacetone with anilines gives N-aryl derivatives of 4-aminopent-3-en-2-one. Similar treatment of benzoylacetone with various primary amines yields N-substituted 3-amino-1-phenylbut-2-en-1-ones. Both series of products with the cis-s-cis-enaminone structure behave as bidentate ligands for PdII to yield stable yellow complexes, the structures of which have been determined as bis(4-anilinopent-3-en-2-onato)- and bis(3-amino-1-phenylbut-2-en-1-onato)-complexes of palladium(II), respectively. To establish the structure of the complex in the solid state, X-ray crystal structure analyses have been carried out on bis[4-(2-bromoanilino)pent-3-en-2-onato]palladium(II). The crystals of the complex solvated by benzene are triclinic and belong to space group P, with cell dimensions a= 8.034(5), b= 11.613(5), c= 7.637(10)A, α= 98.67(5), β= 88.44(5), γ= 100.22(10)°, and Z= 1. The crystal structure has been solved using 2 951 reflections and refined to a final R value of 0.092. The Pd atom takes a square-planar co-ordination and the ligand molecules with the cis-s-cis-enaminone system form six-membered chelate rings with the metal.

Enantioselective Synthesis of (S)-3-(4-Thiazolyl)-2-tert-butoxycarbonylaminopropionic Acid: A Chiral Building Block for Renin Inhibitor

(S)-3-(4-Thiazolyl)-2-tert-butoxycarbonylaminopropionic acid (6), an important structural constituent of the renin inhibitor, has been synthesized from (Z)-3-(4-thiazolyl)-2-benzoylaminoprop-2-enoic acid (4b) by enantioselective hydrogenation using the Ru-(S)-p-tolyl-BINAP complex as the key step, and then followed by acid hydrolysis and tert-butoxycarbonylation.