Kunihiko Takabe

Novel and practical asymmetric synthesis of an azetidine alkaloid, penaresidin B

A novel and efficient asymmetric synthesis of the potent actomyosin ATPase activator, penaresidin B, is described in a short and complete stereoselective manner by featuring the elaboration of the fully functionalized homochiral lactam, which can also be regarded as an advanced intermediate for the synthesis of other azetidine alkaloids.

Novel strategic lipase-catalyzed asymmetrization of 1,3-propanediacetate in supercritical carbon dioxide

Abstract In lipase-catalyzed asymmetrization of 1,3-propanediacetate no enantioselectivity was observed in conventional organic solvents, whereas in supercritical carbon dioxide (scCO2) enantioselectivities were observed up to 50% ee, which probably arose from a conformational changing of lipase at the active site due to a transformation of the amino group of lysine into carbamic acid.

Organocatalytic α-hydroxymethylation of cyclopentanone with aqueous formaldehyde: Easy access to chiral δ-lactones

Optically active lactones are important synthons in perfume and aroma manufacturing. Therefore, developments of efficient asymmetric syntheses are desired. Organocatalytic asymmetric alpha-hydroxymethylations of cyclopentanone with aqueous formaldehyde have been developed, to furnish the corresponding alpha-(hydroxymethyl)cyclopentanone with high enantioselectivity. Further chemical transformation of alpha-(hydroxymethyl)cyclopentanone gave the key intermediate for jasmine lactone, which is widely found in fruits and flowers.

An Efficient and Straightforward Synthetic Process to an Amino Sugar Analogue, Furanodictine B

A convenient and practical strategy for the construction of a natural amino sugar analogue, furanodictine B, isolated from the multicellular fruit body has been developed in an optically active form. The synthetic process is based on readily accessible and stereodefined manipulation of the highly functionalized bicyclic xadderivative incorporating the glucuronolactone-derived skeleton.

Extremely simple and practical synthesis of (±)-vertinolide via the Michael addition

(±)-Vertinolide (1) was synthesized from the readily available tetronic acid derivative 5 in 3 steps. The Michael reaction of the anion derived from 6 with (E)-5-ethoxyocta-1,6-dien-3-one (12) gave the vertinolide precursor 9 in high yield, which was then easily converted to (±)-vertinolide (1).