Nasuo Ueda

Asymmetric synthesis of optically active 2,3-diarylsuccinic acids by oxidative homocoupling of chiral 3-(arylacetyl)-2-oxazolidones

Abstract Oxidative homocoupling of chiral 3-(arylacetyl)-2-oxazolidones 1 was achieved by treatment with DABCO-TiCl4 or DMAP-TiCl4 and afforded the corresponding dimers stereospecifically. The reaction of (4S)- and (4R)-substituted 1 gave (S,S)- and (R,R)-dimers respectively. The obtained dimers were easily transformed to the corresponding 2,3-diaryl succinic acids. This reaction therefore provides a useful method for the synthesis of optically pure 2,3-diarylsuccinic acids. The oxidative coupling was not inhibited by para substitution of an electron donating group on the aryl group. A para-substituted electron withdrawing group and an ortho-substituent, however, hindered the coupling.

Reductive coupling of aromatic oxims and azines to 1,2-diamines using Zn-MsOH or Zn-TiCl 4

Abstract The reduction of aromatic aldoxims and azines with Zn in the presence of MsOH or TiCl 4 afforded N,N′ -unsubstituted 1,2-diamines in one-step. The reductive coupling with Zn-MsOH gave meso 1,2-diamines selectively, whereas dl 1,2-diamines were formed selectively by the reduction with Zn-TiCl 4 .

Electroreductive intramolecular coupling of aromatic δ- and ε-keto esters

Abstract Electroreduction of aromatic δ- and e-keto esters in the presence of chlorotrimethylsilane and triethylamine gave five- and six-membered cyclized products. The products were transformed to the corresponding α-hydroxy ketones.

Stereoselective homocoupling of chiral 1-aroylacetyl-2-imidazolidinones by oxidation with Br2

Abstract The oxidative coupling of sodium enolates of (4 R ,5 S )-1-aroylacetyl-3,4-dimethyl-5-phenyl-2-imidazolidinones with Br 2 as the oxidant affords the R , R -dimers stereoselectively. The R , R -selectivity can be explained by a radical coupling mechanism.

Stereoselective coupling of optically active 3-trans-cinnamoyl-2-oxazolidinones with acid anhydrides by electroreduction

Abstract The electroreduction of chiral 3-trans-cinnamoyl-2-oxazolidinones with acid anhydrides gave β-acylated products stereoselectively. The products were transformed to optically active cis-β,γ-disubstituted-γ-lactones.

The Selective Formose Reaction in Dimethylformamide in the Presence of Vitamin B1

Abstract The formose which was obtained from formaldehyde in the presence of base was a mixture of sugars and sugar alcohols containing over 30 components. The formose reaction has drawn much attention for 122 years from several standpoints; the chemical synthesis of edible carbohydrates from C1 compounds, an important process in the recycling of carbon sources during sustained space flights, and as a model for the prebiotic synthesis of monosaccharides. Nevertheless, because of the complexity of this product mixture (Fig. 1b), the formose reaction has not been completely elucidated and the product (so called formose) has not been useful yet. During the long formose history few products were isolated from the formose mixture and identified, except in work from our laboratories.

A Selective Synthesis of 3,3-Di-C-(hydroxymethyl)-3-deoxy-furanorono-1,4-lactone in the Formose Reaction

Abstract The formose reaction, by which a complex mixture of sugars and sugar alcohols (the so-called formose) are produced by the base-catalyzed condensation of formaldehyde, has received much attention in connection with the prebiotic synthesis of carbohydrates2 and the microbial utilization of formose.3–5 Formose, however, has not been useful yet, because of the complexity of this product mixture (Fig. 1a). Therefore, it seemed desirable to make the reaction more selective.

A convenient synthesis of N-Boc-protected tert-butyl esters of phenylglycines from benzylamines

Abstract The N , N -di-Boc-protected benzylamines undergo [1,2] Boc migration on treatment with KDA/ t -BuOLi. By this reaction, the corresponding N -Boc-protected t -butyl esters of phenylglycines are obtained in high yields.

Stereoselective intramolecular coupling of diaroylacetates of (1R,1′R)-exo,exo′-3,3′-biisoborneol by oxidation with Br2

Abstract The oxidative coupling of diaroylacetate derivatives prepared from (1R,1′R)-exo,exo′-3,3′-biisoborneol with NaH–Br2 gave the corresponding intramolecularly coupled products stereoselectively. The major (R,R)-isomers thus obtained were transformed to (−)-Sesamin and (−)-Eudesmin.

Stereoselective reduction of N-hydroxy-α-iminocarbonyl-oligopeptide methyl esters with Zn–MsOH

Abstract The reduction of N -hydroxy-α-imino esters with Zn–MsOH in THF afforded α-amino esters in high yields. The reduction of N -hydroxy-α-iminocarbonyl-oligopeptide methyl esters prepared from l -phenylalanine and l -leucine di-, tri-, tetrapeptides gave the corresponding S -formed oligopeptide methyl esters in moderate diastereoselectivities.