Kiyosei Iio

ASYMMETRIC TOTAL SYNTHESIS OF FREDERICAMYCIN A

Seventeen years after the isolation of the promising antitumor antibiotic fredericamycin A, the first asymmetric total synthesis of this compound has been accomplished and thereby its absolute configuration established. The key feature is the regiocontrolled [4+2] cycloaddition of 3 to 2, which was obtained by the stereospecific rearrangement of 1. Cp = (-)-camphanoyl.

Total Synthesis of the Antitumor Antibiotic (±)‐Fredericamycin A by a Linear Approach

A linear approach to the total synthesis of racemic fredericamycin A (1) through the oxidative intramolecular [4 + 2] cycloaddition of a (phenylthio)acetylene-cobalt complex is described, which is applicable for the asymmetric total synthesis of naturally occuring 1. The highlight of this work is the aromatic Pummerer-type reaction with 1-ethoxyvinyl chloroacetate, which effects the introduction of the oxygen functional group to the internal B-ring of the highly functionalized, congested polyaromatic ABC-ring moiety.

AN EFFICIENT PREPARATION OF PERI-HYDROXY DIHYDROQUINONE DERIVATIVES THROUGH A PUMMERER-TYPE REARRANGEMENT OF SILYLENE-PROTECTED PERI-HYDROXY AROMATIC SULFOXIDES

Abstract Silylene protection of two dihydroxy groups of the peri -hydroxy aromatic sulfides 6a-f was essential for the subsequent Pummerer-type reaction. The overall process provided a novel and efficient approach to the peri -hydroxy dihydroquinone derivatives 9a-f .

A strong-base induced [4+2] cycloaddition of homophthalic anhydrides with enolizable enones: a direct and efficient synthesis of peri-hydroxy aromatic compounds

A direct and efficient synthesis of peri-hydroxy aromatic compounds via a strong-base induced [4+2] cycloaddition of homophthalic anhydrides with α-phenylsulfinyl enolizable enones has been accomplished.

An efficient synthesis of p-quinones utilizing a novel Pummerer-type rearrangement of p-sulfinylphenols

Treatment of the p-sulfinylphenol derivatives 1 and 5 with trifluoroacetic anhydride causes a Pummerer-type rearrangement on aromatic rings and concomitant desulfurization to give 1 : 1 mixtures of the corresponding p-quinones and p-dihydroquinones, which are subjected to mild oxidation to provide high yields of p-quinones 3 and 7.

Pummerer-type rearrangement on aromatic rings: an unprecedented ipso-substitution of the sulfinyl group of p-sulfinylphenyl ethers into oxygen functional groups leading to protected dihydroquinone derivatives

The treatment of p-(phenylsulfinyl)phenyl ethers 1 with trifluoroacetic anhydride in the presence of styrene selectively caused the direct ipso-substitution of the sulfinyl groups by trifluoroacetoxy groups, giving the protected dihydroquinone derivatives 3 in high to quantitative yields.