Stereoselective synthesis of α,γ -diamino acid esters
摘要:
Chiral didehydro amino acid esters 2/3 derived from amino acids are hydrogenated stereoselectively with rhodium catalysts based on achiral ligands, the alpha,gamma-diamino acid derivatives 4 being the major products. The sense and degree of stereoselectivity can be influenced to some extent by the use of chiral diphosphines. The iridium-containing Crabtree-catalyst is particularly effective in the case of the serine derivative 2 (R1 = HOCH2).
Cycloaddition reactions of λ-amino α,β-didehydro amino acid esters: a test case for the principle of 1,3-allylic strain
摘要:
N,N-Dibenzylainino aldehydes, readily accessible from amino acids, can be converted into gamma-N,N-dibenzylamino alpha,beta-didehydro amino acid esters without racemization; these undergo stereoselective Diels-Alder reactions and 1,3-dipolar cycloaddition with diazomethane, the sense of diastereoselectivity being opposite to that predicted by the conventional principle of 1,3-allylic strain.