Synthesis of oxaspiro[m.n] skeletons based on the Nicholas reaction

Activation of olefins via asymmetric Brønsted acid catalysis

The activation of olefins for asymmetric chemical synthesis traditionally relies on transition metal catalysts. In contrast, biological enzymes with Brønsted acidic sites of appropriate strength can protonate olefins and thereby generate carbocations that ultimately react to form natural products. Although chemists have recently designed chiral Brønsted acid catalysts to activate imines and carbonyl compounds, mimicking these enzymes to protonate simple olefins that then engage in asymmetric catalytic reactions has remained a substantial synthetic challenge. Here, we show that a class of confined and strong chiral Brønsted acids enables the catalytic asymmetric intramolecular hydroalkoxylation of unbiased olefins. The methodology gives rapid access to biologically active 1,1-disubstituted tetrahydrofurans, including (-)-Boivinianin A.

Synthesis and structural revision of (+/-)-laurentristich-4-ol

The structure of tetracyclic natural sesquiterpene laurentristich-4-ol was revised based on its synthetic studies. The proposed and the revised structures of laurentristich-4-ol were both synthesized with SmI(2)-mediated ketyl radical cyclization as the key step to construct the spirocyclic ether skeleton.

[Development of highly selective reactions based on metal carbonyls and its application to synthesis of bioactive compounds]

Alkynes react with commercially available Co2 (CO)8 to give the corresponding alkyne-Co2 (CO)6 complexes. Similarly, treatment of arenes with Cr(CO)6 produces arene-Cr (CO)3 complexes. By taking advantage of the intriguing properties of these metal carbonyl complexes, we developed some selective reactions. In this review, the following topics are discussed: (i) development of selective reactions based on alkyne-Co2 (CO)6 complexes; (ii) development of selective reactions based on arene-Cr (CO)3 complexes; and (iii) their application to syntheses of bioactive compounds.