57293-25-1Relevant academic research and scientific papers
Indium tribromide-promoted arene-terminated epoxy olefin cyclization
Zhao, Jun-Feng,Zhao, Yu-Jun,Loh, Teck-Peng
, p. 1353 - 1355 (2008/12/21)
An arene-terminated epoxy olefin cyclization was promoted by a water-tolerant Lewis acid to give tri- and tetracyclic 3β-hydroxy terpenoids and steroid derivatives in 57 and 37% yields, respectively, per new formed ring up to 75%. The Royal Society of Chemistry.
Enantio- and diastereoselective stepwise cyclization of polyprenoids induced by chiral and achiral LBAs. A new entry to (-)-ambrox, (+)-podocarpa-8,11,13-triene diterpenoids, and (-)-tetracyclic polyprenoid of sedimentary origin
Ishihara, Kazuaki,Ishibashi, Hideaki,Yamamoto, Hisashi
, p. 3647 - 3655 (2007/10/03)
An enantio- and diastereoselective stepwise cyclization of polyprenoids induced by Lewis acid-assisted chiral Bronsted acids (chiral LBAs) and achiral LBAs is described. In particular, the absolute stereocontrol in the initial cyclization of polyprenoids to form an A-ring induced by chiral LBAs and the importance of the nucleophilicity of the internal terminator in polyprenoids for the relative stereocontrol in subsequent cyclization are demonstrated. (-)-Ambrox was synthesized via the enantioselective cyclization of (E,E)-homofarnesyl triethyrsily ether with triethylsilyl ether with tin(IV) chloride-coordinated (R)-2-(o-fluorobenzyloxy)-2′-hydroxy-1,1′-binaphthyl ((R)-BINOL-o-FBn) and subsequent diastereoselective cyclization with CF3CO2H·SnCl4 as key steps. Protection of (E,E)-homofarnesol by a triethylsilyl group increased the enantioselectivity of chiral LBA-induced cyclization and both the chemical yield and diastereoselectivity in the subsequent cyclization. The enantioselective cyclization of homo(polyprenyl)arenes possessing an aryl group was also induced by (R)-BINOL-o-FBn·SnCl4. Several optically active podocarpa-8,11,13-triene diterpenoids and (-)-tetracyclic polyprenoid of sedimentary origin were synthesized (75-80% ee) by the enantioselective cyclization of homo(polyprenyl)benzene derivatives induced by (R)-BINOL-o-FBn·SnCl4 and subsequent diastereoselective cyclization induced by BF3-Et2O/EtNO2 or CF3CO2H·SnCl4.
