A New Artificial Cyclase for Polyprenoids: Enantioselective Total Synthesis of (−)-Chromazonarol, (+)-8-<i>e</i><i>pi</i>-Puupehedione, and (−)-11‘-Deoxytaondiol Methyl Ether
pure 3-o-fluorobenzyloxy-2-hydroxy-2'-(p-methoxybemzyl)-1,1'-binaphthyl.SnCl4, which is effective for the enantioselective cyclization of 2-(polyprenyl)phenol derivatives to afford polycyclic terpenoids bearing a chroman skeleton such as (-)-chromazonarol, (+)-8-epi-puupehedione, a key synthetic intermediate of (+)-wiedendiol, and (-)-11'-deoxytaondiol methyl ether.
Electrophilic halogenation is used to produce a wide variety of halogenated compounds. Previously reported methods have been developed mainly using a reagent‐based approach. Unfortunately, a suitable “catalytic” process for halogen transfer reactions has yet to be achieved. In this study, arylamines have been found to generate an N‐halo arylamine intermediate, which acts as a highly reactive but selective catalytic
Lewis Acid-Promoted Intermolecular Acetal-Initiated Cationic Polyene Cyclizations
作者:Yu-Jun Zhao、Shu-Sin Chng、Teck-Peng Loh
DOI:10.1021/ja067660+
日期:2007.1.1
This paper describes a highly efficient intermolecular biomimeticpolyenecyclization method using acetal as initiators. Both good yield and asymmetricinduction were obtained.
[reaction: see text] New Lewis acid-assisted Bronsted acids (LBAs), tin(IV) chloride-2,6-dialkoxyphenols, serve as artificial cyclases for biomimeticpolyenecyclization. For example, the enantioselective cyclization of 4-(homogeranyl)toluene using tin(IV) chloride-2,6-di[(1'R,2'R)-trans-2'-(3' ',5' '-xylyl)cyclohexanoxy]phenol gave a trans-fused tricyclic compound with 85% ee.
NXS, Morpholine, and HFIP: The Ideal Combination for Biomimetic Haliranium-Induced Polyene Cyclizations
作者:Andreas M. Arnold、Alexander Pöthig、Markus Drees、Tanja Gulder
DOI:10.1021/jacs.8b00113
日期:2018.3.28
contrast to Nature that accomplishes polyenecyclizations seemingly with ease, such transformations are difficult to conduct in the lab. In our program dealing with the development of selective halogenations of alkenes, we now asserted that standard X+ reagents are perfectly suited for the biomimetic cation-π cyclization of both electron rich and poor linear polyenes in the presence of the Lewis base