Synthesis of Non-natural, Frame-Shifted Isoprenoid Diphosphate Analogues
作者:Kayla J. Temple、Elia N. Wright、Carol A. Fierke、Richard A. Gibbs
DOI:10.1021/acs.orglett.6b02977
日期:2016.12.2
A set of synthetic approaches was developed and applied to the synthesis of eight frame-shifted isoprenoid diphosphate analogues. These analogues were designed to increase or decrease the methylene units between the double bonds and/or the pyrophosphate moieties of the isoprenoid structure. Evaluation of mammalian GGTase-I and FTase revealed that small structural changes can result in substantial changes
palladium/XPhos complex and 5-norbornene-2-carboxylic acid was developed. This system promotes a two-component annulation reaction, allowing the construction of tetrahydronaphthalenes and indanes that contain quaternary centers through consecutive Catellani-type C–H activation and redox-relay Heck reaction. Inexpensive 5-norbornene-2-carboxylic acid acts as a catalytic mediator (20 mol %) in this process. This mild
Synthetic applications of homoiodo allylsilane II. Total syntheses of (−)-andrographolide and (+)-rostratone
作者:Hai-Tao Gao、Bian-Lin Wang、Wei-Dong Z. Li
DOI:10.1016/j.tet.2014.10.015
日期:2014.12
The first total synthesis of (−)-andrographolide (1), an ent-Labdane diterpenoid lactone from Asian medicinal herb Andrographis paniculata, was achieved via the biomimetic cyclization of an epoxy homoiodo allylsilane precursor 7. Asymmetric total synthesis of (+)-rostratone (25), an antipodal Labdane diterpenoid, was also accomplished via similar biomimetic cyclization of a readily accessible epoxy
Mediators play a central role in Catellani-type reactions. Herein we reported the discovery of inexpensive 5-norbornene-2-carboxylic acid (N-4) as a general catalytic mediator (20 mol%) to facilitate ortho C-H activation and the following C-C bond formation of aryl iodides. Firstly, a cooperative catalytic system comprising N-4 and a palladium/XPhos complex was developed for the novel Catellani/redox-relay Heck cascade to construct tetrahydronaphthalenes and indanes that contain a quaternary carbon stereogenic center. The striking feature of this work was the avoidance of stoichiometric NBE mediator that are usually required for Catellani-type reactions. Then, preliminary results demonstrated that N-4 could act as a general catalytic mediator to replace NBE for other Catellani-type reactions, which will undoubtedly inspire future developments in the field of cooperative catalysis. Finally, control experiments indicated that the carboxylic acid moiety of N-4 plays an essential role in its ability to serve as a superior mediator. (C) 2019 Elsevier Ltd. All rights reserved.
Synthesis of Frame-Shifted Farnesyl Diphosphate Analogs
作者:Andrew T. Placzek、James L. Hougland、Richard A. Gibbs
DOI:10.1021/ol300683r
日期:2012.8.17
A set of synthetic approaches were developed and applied to the synthesis of eight frame-shifted farnesyl diphosphate (FPP) analogs. These analogs bear increased or decreased methylene units between the double bonds and/or diphosphate moieties of the isoprenoid structure. Evaluation versus mammalian FTase revealed that small structural changes can lead to dramatic changes in substrate ability.