Hisanaka Ito

Asymmetric Claisen rearrangement

Development of the asymmetric Claisen rearrangement is one of the challenging tasks in synthetic organic chemistry. There have been numerous reports of the asymmetric Claisen rearrangement based on the intramolecular chirality transfer using chiral substrates. On the other hand, reactions of achiral substrates with an external chiral activator have been studied during the last decade. In this review article, recent advances in the asymmetric Claisen rearrangement are described.

Preparation and regio- and diastereoselective reactions of allylic zirconium reagents from allylic ether derivatives

Abstract Allylic zirconium reagents were generated by treating allylic ether derivatives with zirconocene “Cp 2 Zr”. The allylic zirconium reagents reacted with aldehydes in highly regio- and diastereoselective manner to give homoallylic alcohol compounds.

Generation of allylic and related organozirconiums through a highly effective zirconium—β-alkoxide elimination reaction

Abstract Reactions and characterization of allylic and related zirconium reagents (allenic and γ-alkoxyallylic zirconiums) generated by treatment of allylic and/or propargylic ethers with a zirconocene-butene complex (“Cp 2 Zr”) are described.

Zirconium-mediated diastereoselective coupling reactions of chiral aldimine : remarkable temperature-dependence of chiral induction

Zr-Mediated coupling reactions of aldehyde with chiral aldimine which is derived from benzaldehyde and (R)-phenylglycinol methyl ether showed a remarkable temperature effect on the sense of chiral induction to yield amino alcohol derivatives with high diastereoselectivities.

Preparation and reactions of allenic zirconium species from propargylic ether derivatives

Abstract The generation of allenic zirconium intermediates by treating propargylic ether derivatives with “Cp 2 Zr” and their reactions with aldehydes in the presence of borontrifluoride etherate yield anti-β-acetylenic alcohols along with α-allenic alcohols.

Asymmetric Diels–Alder reactions of 2-fluoroacrylic acid derivatives. Part 1: The construction of fluorine substituted chiral tertiary carbon

Abstract For the construction of chiral monofluorinated tertiary carbons, we have examined the asymmetric Diels–Alder reaction of 2-fluoroacrylic acid derivatives bearing a chiral oxazolidinone moiety. Under diethylaluminum chloride catalyzed conditions at −100°C, the reaction of 1 with isoprene proceeded smoothly with high diastereoselectivity.

Enantioselective synthesis of curacin A. 1. Construction of C1–C7, C8–17, and C18–C22 segments

Abstract Total synthesis of curacin A, a novel antimitotic antiproliferative antibiotic, was achieved by the connection of C1C7, C8C17, and C18C22 segments. Enantioselective preparation of each segments were accomplished by asymmetric allylation, chiral synthon method, and asymmetric hydrolysis by using pig liver esterase, respectively.

Asymmetric Diels–Alder reactions of 2-fluoroacrylic acid derivatives. Part 2: A remarkable effect of fluorine substituent on the diastereoselectivity

Abstract An efficient construction of a chiral monofluorinated tertiary carbon was achieved by a highly exo - and diastereofacial selective Diels–Alder reaction of a 2-fluoroacrylic acid derivative derived from 8-phenylmenthol, and cyclopentadiene. The substituent effect of the fluorine on the selectivities is remarkable as compared with the other substituents at the α-position of the acrylate.

Enantioselective aromatic Claisen rearrangement

Abstract The development of a highly enantioselective aromatic Claisen rearrangement was achieved by the reaction of catechol mono allylic ethers with chiral boron reagent 1 . This system was also shown to avoid the formation of para rearrangement and abnormal Claisen rearrangement products.

Toward the synthesis of didemnaketal B: a convergent synthesis of the C9-C28 subunit.

Synthesis of the C9-C28 subunit of didemnaketal B has been developed. This subunit was convergently prepared from four chiral synthons and at the longest linear sequence required 16 steps.