Shinji Nagumo

Alkylation of 4-hydroxyproline ester derivatives. Diastereoselectivity guided by the anomeric effect and π-interaction

Abstract The alkylation of 4-hydroxyproline derivatives 7 and 1 2 with a range of alkylating reagents was examined. The stereoselectivity was found to be dependent on the reagent and the N-protecting group. This was explained by a concept based on the stereoelectronic effect and π-interaction.

Synthesis of (−)-TAN1251A using 4-hydroxy-l-proline as a chiral source

Abstract A new synthetic route of (−)-TAN1251A possessing an antimuscarinic activity was developed on the basis of alkylation of a trans-4-hydroxy- l -proline derivative and the subsequent construction of an azaspiro ring as key steps.

Total synthesis of (±)-TAN1251A

Abstract The first synthesis of novel type alkaloid (±)-TAN1251A possessing an antimuscarinic activity was achieved.

Total synthesis of (-)-oudemansin X based on enzymatic resolution using immobilized lipase

Abstract (−)-Oudemansin X ( 1 ) was synthesized based on enzymatic resolution of (±)-diol 5 using immobilized lipase.

7-endo Selective Friedel-Crafts type cyclization of vinyloxiranes linked to an ester group

Abstract Treatment of arylpropyl vinyloxiranes linked to ester with BF3 was found to produce seven-membered ring products in excellent yields. This reaction proceeded in an inversion fashion.

Total synthesis of antimuscarinic alkaloid, (±)-TAN1251A

Abstract The total synthesis of (±)-TAN1251A possessing an antimuscarinic activity was achieved. Carboxylic acid ( 1 ) was converted into carbamate ( 3 ) through a sequence of alkylation and Curtius rearrangement. After a few functional group interconversions of 3 , the corresponding amine ( 9 ) was converted into an azaspiro molecule ( 18 ) through cyclization and installation of a C 2 unit. Hydrolysis of 18 followed by lactam formation afforded tricyclic compound ( 20 ). Coupling of 20 with aldehyde ( 22 ) gave two epimeric adducts, ( 23A ) and ( 23B ), which were converted into TAN1251A by four steps.

Novel ring cleavage based on intermolecular aldol condensation

Abstract Ring cleavage and reconstruction via intramolecular aldol condensation followed by Grob fragmentation under acetalization conditions (BF 3 /ethylene glycol) was developed into a novel ring cleavage based on intermolecular aldol condensation. On the basis of this reaction, (R,R)-3,5-dimethylcyclohexanone was converted into the chiral straight-chain compound with syndiotactic methyl function. The ring cleavage reaction based on a crossed intermolecular aldol condensation was also examined, and the reaction pathway was discussed.

Total synthesis and structural revision of sekothrixide.

The first total synthesis of 14-membered macrolide sekothrixide and the originally proposed structure are reported. Seven contiguous asymmetric centers in the side chain were constructed using ring-openings of several kinds of epoxide. Assembly of the left segment and right segment was performed on the basis of the RCM reaction to generate 14-membered lactones having an E-trisubstituted olefin. These synthetic results led to a revision of C4, C6, and C8 stereochemistry in the structure of natural sekothrixide.

Drastic conversion of bicyclo[m,n,0]alkane rings to spirocyclic skeletons

Abstract Under acetalization conditions (BF 3 /ethylene glycol), bicyclo[m.n.0]alkanones with the carbonyl function at 3′ or 4′-position of the C 1 -side chain undergo the ring cleavage to build up the spirocyclic skeletons.

Novel skeletal rearrangement of hydroindan derivatives into hydroazulenones via an alkoxy radical

A novel construction of hydroazulenones using skeletal rearrangement of epoxy-hydroindan derivatives via alkoxy radical was developed. The reaction was also found to proceed without damage of acetal or olefin group.