Showing papers by "Nobuaki Taniguchi published in 1993"

Synthesis of polycyclic cyclobutane derivatives by tandem intramolecular Michael-aldol reaction under two complementary conditions: TBDMSOTf-Et3N and TMSI-(TMS)2NH

Abstract: The treatment of α,β-unsaturated esters having a ketone function at an appropriate position with either TBDMSOTf in the presence of Et 3 N or TMSI in the presence of (TMS) 2 NH provided, via a tandem intramolecular Michael-aldol reaction sequence, several different types of cyclobutane derivatives. The two reaction conditions were complementary. Tricyclo[4.2.1.03-8]nonanes 34 and 35, tricyclo[5.1.1.0 3,8 ]nonane 40, tricyclo[5.4.0.0 3,7 ]undecane 51, tetracyclo[5.4.0.0 3,7 .0 9,11 ]undecane 45, and the bicyclo[3.2.0]heptanes 36, 57, and 38, which have structures either partially or completely similar to those of endiandric acids A (1a), B (1b), and C (2), trihydroxydecipiadiene (3), lintenone (4), italicene (3), and filifolone (6), were stereoselectively synthesized by the tandem reaction

Deconjugation of α,β-unsaturated esters and an intramolecular Michael reaction of bis-α,β-unsaturated esters with trialkylsilyl trifluoromethanesulfonate in the presence of tertiary amine: synthesis of (±)-ricciocarpin A

Abstract: Treatment of the α,β-unsaturated esters 1, 6 and 8 with trialkylsilyl trifluoromethanesulfonate in the presence of a tertiary amine gave, via silyl dienol ethers, the corresponding deconjugated esters 3, 7 and 9 as the major products, respectively. Reaction of bis-α,β-unsaturated esters 12a and 12b with a trialkylsilyl trifluoromethansulfonate in the presence of a tertiary amine caused an intramolecular Michael reaction to produce the cyclopentanes 14a and 20a and the cyclohexanes 14b and 20b. Bicyclic compounds 21a and 21b formed by tandem Michael–Dieckmann or intramolecular Diels–Alder reaction were concurrently obtained. The cyclohexane derivative 14b was converted into the racemate of a sesquiterpene, (±)-ricciocarpin A 22.

Synthesis of potentially useful intermediates for 1-fluorocarbapenems

Abstract: The displacement reaction of the 4-acetoxyazetidin-2-one (6) with dimethyl fluoromalonate was readily performed in the presence of lithium hexamethyldisilazide. The product (7), quantitatively obtained, was converted into two potential synthetic intermediates (4) and (5) of 1-fluorocarbapenem derivatives

A novel rearrangement of cyclobutanes to cyclopropanes; construction of tricyclo[5.4.0.0]undecane and bicyclo[4.1.0]heptane systems

Abstract: Treatment of hydroxylated cyclobutane derivatives with BF3·OEt2, POCl3 in the presence of pyridine or Raney nickel causes a novel rearrangement forming tricycle[5.4.0.0]undecane and bicyclo[4.1.0]heptane systems.

Intramolecular Michael reaction using trialkylsilyl trifluoromethanesulfonates and tertiary amine system: total synthesis of (±)-ricciocarpin A

Abstract: Intramolecular Michael reaction of bis-α,β-unsaturated esters 1 forming 2 was carried out by the action of a trialkylsilyl trifluoromethanesulfonate in the presence of a tertiary amine; the product was transformed into ricciocarpin A 8.