Hetero-Diels–Alder and pyroglutamate approaches to (2S,4R)-2-methylamino-5-hydroxy-4-methylpentanoic acid
作者:James E. Tarver、Kristen M. Terranova、Madeleine M. Joullié
DOI:10.1016/j.tet.2004.08.089
日期:2004.11
protected (2S,4R)-2-methylamino-5-hydroxy-4-methylpentanoic acid, a non-coded amino acid of cyclomarin A, and its diastereomer are reported. A pyroglutamate template was employed in the key diastereoselective alkylation used for introducing the 4-methyl stereochemistry. In addition, the first diastereoselective intramolecular hetero-Diels–Alder of a 2-cyano-1-azadiene with an electron deficient dienophile
Chiral monooxazolines as modular copper(I)-heterocomplex building blocks: investigations on the catalytic asymmetric cyclopropanation of alkenes
作者:Elisabete P. Carreiro、J.P. Prates Ramalho、Anthony J. Burke
DOI:10.1016/j.tet.2011.04.066
日期:2011.6
synthesized in good yields. The catalytic activity of these monodentate oxazoline/Cu catalysts was evaluated in the catalytic asymmetric cyclopropanation of styrene and α-methylstyrene, giving moderate to good enantioselectivities (up to 74% ee for the trans-cyclopropane product) and full conversions (up to 100%). In an attempt to enhance the enantioselectivities of the cyclopropanations, heterocombinations of