Claisen-rearrangement-mediated ring contraction of macrocyclic lactones
作者:Raymond L. Funk、Matthew M. Abelman、John D. Munger
DOI:10.1016/s0040-4020(01)90572-1
日期:——
Macrocyclic ketene acetals 3 undergo Claisenrearrangements smoothly and constitute a viable and general approach to hetero- or carbocyclic ring systems 4. This novel ring contraction process is subject to high internal asymmetric induction (cf. lactones 7 → carbocycles 8) as well as relative asymmetric induction in the rearrangements of ketene acetals derived from lactones 18, 23 and 27. Finally,
A concise and versatile syntheses of 11-16-membered macrolides and 13-15-membered macrolactams have been achieved using a Tsuji-Trost type reaction. This approach is composed of intramolecular cyclization employing ethyl carbonate with carboxylic acids and catalytic amount of Pd(PPh3)4 to form carbon-heteroatom covalent bonds with no use of stoichiometric reagents.