An asymmetric synthesis of cis-4-t-butyldimethylsiloxy-2-cyclopenten-1-ol and cis-4-tetrahydropyranyloxy-2-cyclopenten-1-ol, versatile chiral synthetic intermediate for prostanoids

A base-mediated aerobic oxidative synthesis of cyclopent-2-enol derivatives from doubly activated cyclopropanes and substituted acetonitriles

We report here that polysubstituted cyclopent-2-enols can be constructed by the one-pot reaction of doubly activated cyclopropanes and α-EWG substituted acetonitriles under mild basic conditions via a domino-ring-opening-cyclization/deacylation/oxidation sequence. Moreover, the synthetic applications of these cyclopent-2-enols have been demonstrated in the late-stage derivatization into functionalized cyclopentapyrimidin-4-ones and 2-hydroxy cyclopentanones with good yields.

Chiral Lithium Amides: Tuning Asymmetric Synthesis on the Basis of Structural Parameters

An overview on the structural arrangements adopted by Chiral Lithium Amides (CLAs), alone or in mixed complexes, is presented. These species are important reagents for asymmetric synthesis and understanding their organization is essential to improve their design and the reaction conditions.

A Failed Late-Stage Epimerization Thwarts an Approach to Ineleganolide

Significant efforts were made to complete a synthesis of the complex norcembranoid ineleganolide via a seemingly attractive strategy involving late-stage creation of the central seven-membered ring. While the two key enantioenriched building blocks were made via high-yielding sequences and their convergent union was efficient, the critical C4-C5 bond of this sterically congested natural product could never be forged. Several interesting examples of unexpected acid-base behavior and unanticipated proximity-induced reactivity accounted for most of the problems in the execution of the synthesis plan.

An experimental and theoretical study of the enantioselective deprotonation of cyclohexene oxide with isopinocampheyl-based chiral lithium amides

The mechanism of the enantioselective deprotonation of cyclohexene oxide with isopinocampheyl-based chiral lithium amide was studied by quantum chemical calculations. The transition states of eight molecules were fully optimized at the ab initio HF/3-21G and density functional B3LYP/3-21G levels with Gaussian 98. The activation energies were calculated at the B3LYP/6-31+G(3df,2p)//B3LYP/3-21G level. We found the theoretical evaluation to be consistent with the experimental data. At the best case, an enantiomeric excess of up to 95% for (R)-2-scyclohexen-1-ol was achieved with (−)-N, N-diisopinocampheyl lithium amide.

Design, Synthesis, and Application of Chiral Nonracemic Lithium Amide Bases in Enantioselective Deprotonation of Epoxides

The reaction of epoxides with chiral nonracemic lithium amide bases, designed and prepared from (R)-phenylglycine, has been studied in detail. A maximum of 80% ee was obtained for conversion of cyclohexene oxide to (S)-2-cyclohexen-1-ol. Enantioselective deprotonation of a variety of other epoxides was studied. A cyclopentanoid core unit for prostaglandin synthesis was synthesized in 97% ee.

Analytical and preparative resolution of enantiomers of prostaglandin precursors and prostaglandins by liquid chromatography on derivatized cellulose chiral stationary phases

Analytical methods were developed for the separation of the enantiomers of four cyclopentenone precursors of prostaglandins. The resolution obtained is correlated with the chemical environment around the chiral center of the cyclopentenones. The analytical methods were scaled up to preparative loadings and the chromatographic parameters were varied to determine their effect on the preparative separations. The correlation between analytical resolution and preparative resolution was also investigated. In addition to the precursors, the preparative resolution of the enantiomers of a synthetic prostaglandin analogue was investigated.

Preparative resolution of enantiomers of prostaglandin precursors by liquid chromatography on a chiral stationary phase

Preparative liquid chromatographic methods were developed for the chiral resolution of two different cyclopentenone precursors of a synthetic prostaglandin. Various solvent combinations of alcohols and alkanes were investigated to determine the method which has the greatest throughput. The effect of particle size on the chiral resolution was also investigated. In addition, the preparative system was automated to allow for unattended operation for up to 10 h.