Total Synthesis of (+)-Laurencin: An Asymmetric Alkylation−Ring-Closing Metathesis Approach to Medium Ring Ethers
作者:Michael T. Crimmins、Kyle A. Emmitte
DOI:10.1021/ol991201e
日期:1999.12.1
enantioselective total synthesis of (+)-laurencin 1 is achieved in 18 steps from (S)-(+)-4-benzyl-3-benzyloxyacetyl-2-oxazolidinone. The key steps in this synthesis are an asymmetric glycolate alkylation leading to acyl oxazolidinone 2 and a subsequent ring-closing olefin metathesis to construct the oxocene core of 1. The approach to medium ring ethers utilized in this synthesis provides a general and efficient
Highly Stereoselective and Efficient Total Synthesis of (+)-Laurencin
作者:Seungyoup Baek、Hyunil Jo、Hansoo Kim、Hyoungsu Kim、Sanghee Kim、Deukjoon Kim
DOI:10.1021/ol047877d
日期:2005.1.1
A highlystereoselective and efficient asymmetric totalsynthesis of (+)-laurencin (1) has been accomplished from the known oxazolidinone 5 in 15 steps. The route features an efficient internal alkylation to form oxocene 3 from 4 and a novel use of acetonitrile anion as a two-carbon acetaldehyde equivalent for direct synthesis of ketone 2 from alpha-alkoxy amide 3.
Laurencin was efficiently synthesized from a C-glycosidederivative based on ring expansion of the oxane part of the starting compound into an eight-membered cyclic ether via a ring-cleavage/ring-closing olefin metathesis process, stereoselective introduction of a bromo group at C4, and convergent construction of the side-chain part using a lithiated enyne unit.
The first total synthesis of (+)-laurencin (1), which is the most representative marine natural product isolated from red algae, is described via intermediates 2–18. Key steps in the synthesis include a facile oxidative preparation of 2, an effective conversion of 9a to 11, and a SmI2-catalyzed elongation reaction of 15, providing 16a.