Yoshiro Hirai

An efficient synthesis of (-)-bulgecinine

Abstract A highly stereoselective synthesis of (-)-bulgecinine ( 1 ) via the pyrrolido[1,2- c ]oxazolidin-3-one system ( 2 ) has been achieved by starting with the asymmetric epoxidation of the twin allyl alcohol system ( 6 ). The transformation of note includes the palladium-catalyzed N →π cyclization leading exclusively to a trans -2,5-disubstituted pyrrolidine.

Regioselective demethylation of 2,6-dimethoxybenzaldehydes with magnesium iodide etherate

Abstract Demethylation of asymmetically substituted 2,6-dimethoxybenzaldehydes with magnesium iodide etherate regioselectively single 6-methoxysalicylaldehydes derived from the more unstable chelation.

Total synthesis of SS20846A via intramolecular Pd(II)-catalyzed cyclization

Abstract A stereoselective total synthesis of SS20846A was efficiently accomplished by means of an intramolecular palladium(II)-catalyzed cyclization.

A new preparation of 2,5-dihydro-1-benzoxepins using Mitsunobu cyclization, and the synthesis of natural radulanins

Abstract Mitsunobu cyclization of o -[4-hydroxy-3-methyl-2( Z )-butenyl]phenol 2a effected selective seven-membered cyclization to give 3-methyl-2,5-dihydro-1-benoxepin 1a . Using this procedure, natural radulanin A and radulanin A methyl ether were synthesized effectively.

Palladium(II)-catalyzed stereocontrolled cyclization via hemiacetal intermediates: Total synthesis of 5-epi-prelactone C

Palladium(II)-catalyzed cyclization of 3,7-dihydroxy-4-methyl-5-octenal derivative was carried out to give 2,3,4,6-tetrasubstituted tetrahydropyran with stereoselective 1,3-chirality transfer in net retention of stereochemistry. The cyclized product was converted into 5-epi-prelactone C.

PALLADIUM(II)-CATALYZED CYCLIZATION OF URETHANES AND ITS APPLICATION TO A TOTAL SYNTHESIS OF 1-DEOXYNOJIRIMYCIN

We have employed a palladium(II)-catalyzed cyclization of allylic alcohol as a key reaction to achieve a total synthesis of the azasugar 1-deoxynojirimycin from D-mannitol. This reaction should be useful for the stereoselective construction of natural poly-substituted piperidine derivatives.

Regioselective cyclization of m-acylaryl 1,1-dimethylpropargyl ethers giving 5-acyl-2,2-dimethyl-2H-chromenes

Abstract Thermal cyclization of some m -acylaryl 1,1-dimethylpropargyl ethers ( 1a – f ) effected regioselective ortho cyclization giving the corresponding 5-acyl-2,2-dimethyl-2 H -chromenes ( 2a – f )

A novel approach to (+)-yohimbine

Abstract The synthesis of (+)-yohimbine was achieved by the reaction sequence involving the asymmetric intramolecular Michael reaction to form the D-ring piperidine system and subsequent formation of the E ring skeleton followed by regio- and stereo-selective introduction of the methoxycarbonyl and hydroxyl on the ring E.

AN ENANTIOSELECTIVE CONSTRUCTION OF PYRROLIDONES BEARING FUNCTIONALIZED APPENDAGES VIA AN ASYMMETRIC INTRA-MOLECULAR MICHAEL REACTION

Synthesis of pyrrolidones via an intramolecular Michael reaction of acyclic compounds using 1-phenylethylamine as a mediator

Pd(II)-Catalyzed Cyclization to Ether and Its Application to the Synthesis of the trans-Fused Polyether Core

We employed an iterative Pd(II)-catalyzed cyclization reaction to ether from tri-O-acetyl-D-glucal to synthesize trans-fused polyethers. This approach should be applicable to synthesize the core structure of marine ladder toxins.