Yoko Yuasa

Diastereoselective Synthesis of Cyclic Ethers by Radical Cyclization at β-Position of β-Alkoxyacrylates

Abstract Regioselective carbon-carbon bond formation by radical reaction at the β-position of β-alkoxyacrylate was applied to a synthesis of 2,5-disubstituted tetrahydrofuran, 2,6-disubstituted tetrahydropyran, 2,7-disubstituted oxepane derivatives.

Synthesis of b-Oxygenatd g-amino Acids and g-Oxygenated g-Amino Acids from a-Amino Acids

A diastereoselective synthesis of 2-amino alcohols toward a synthesis of β-oxygenated γ-amino acids, γ-oxygenated δ-amino acids, and related compounds was summarized

Diastereoselective synthesis of 2,5-disubstituted 3-hydroxypyrrolidine and 2,6-disubstituted 3-hydroxypiperidine derivatives by radical cyclisation; synthesis of (+)-bulgecinine and (–)-desoxoprosopinine

Cyclisation of the O-stannyl ketyl, generated from the aldehyde 17 by reaction with tributyltin hydride in the presence of AIBN, gives the 5-benzyloxymethyl-7-hydroxypyrrolooxazolidin-2-ones as a diastereoisomeric mixture of 7α-ol 18 and 7β-ol 19 (2 : 1), with high diastereoselectivity with respect to the 5,7a positions. (+)-Bulgecinine 8 is enantioselectively synthesised by stereospecific reduction of the ketone 20, derived from compounds 18 and 19. In a similar way, cyclisation of compound 40 gives a 2 : 1 mixture of compounds 41 and 42. Conversion of compound 41 into (–)-desoxoprosopinine 9 is successfully achieved.

A Synthesis of Heterocyclic Fused Isoquinolines Through N-Acyliminium Ion Intermediates

Abstract Conversion of terminal olefin to formyl group by ozonolysis was applied to a new generation of N-acyliminium ions and several kinds of heterocyclic fused isoquinolines were prepared.

Enantioselective Synthesis of (−)-desoxoprosopinine by radical cyclization

Abstract Reaction of the aldehyde 12 with tributyltin hydride in the presence of AIBN gave a mixture of 13 as a 2:1 mixture of 8β-ol and 8α-ol. Conversion of 14 , derived from 13 , to (−)-desoxoprosopinine 3 was successfully achieved.

Diastereoselective synthesis of 2,6-disubstituted 3-hydroxy piperidine derivatives by an application of radical cyclization

N-[α-(2-bromo-1-butenyl)-α-methyl]oxazolin-2-one (7) and N-[α-(2-bromo-1-butenyl)-α-pyranyloxyethyl]oxazolin-2-one (14), obtained by starting with ethyl acetoacetate, were treated with tributyltin hydride in the presence of AIBN afforded the cyclisation products (8) and (15),respectively, with high diastereoselectivity

Diastereoselective Synthesis of 2,6-Disubstituted 3-Hydroxypiperidine, 2-(a-Hydroxyalkyl)-3-hydroxypiperidine and 2-(a-Hydroxyalkyl)-3-hydroxypyrrolidine Derivatives

Reduction of 5-substituted 5,8a-trans-oxazolo[3,4-a]pyridin-8-ones (7a,b), obtained by an application of α-acylamino radical cyclization at the initial stage, with NaBH 4 and K-Selectride was found to proceed with complete stereocontrol in all cases

Highly diastereoselective synthesis of N-Boc dolaisoleuine, unusual amino acid in dolastatin 10

Photolysis of 5-phenylthiooxazolidin-2-one (4) in the presence of (n-Bu 3 Sn) 2 and n-Bu 3 SnCH 2 CH=CH 2 afforded 5-allyl derivative (5) which was led to N-Boc dolaisoleuine (11), one component of dolastatine 10 (2), via 6-10

A facile and efficient stereoselective synthesis of 6-hydroxy-trans-4a-phenyldecahydroisoquinoline

Abstract A stereoselective synthesis of 6-oxygenated trans -4a-phenyldecahydroisoquinoline was achieved by treatment of 1-ethoxycarbamoyl-1-phenyl-1,4-hexadiene with paraformaldehyde in formic acid.

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.