Synthesis of alpha-cyclopropyl-beta-homoprolines.
1-(2-Pyrrolidinyl)cyclopropanecarboxylic acids (alpha-cyclopropyl-beta-homoprolines) were prepared by 1,3-dipolar cycloadditions of cyclic nitrones onto bicyclopropylidene followed by trifluoroacetic acid induced thermal fragmentative rearrangement. With the use of enantiopure pyrroline N-oxides derived from easily available chiral pool molecules, beta-homoprolines were formed with high stereocontrol. The incorporation of one of these new cyclic beta-amino acids into a simple tripeptide was also evaluated. In particular, the sterically hindered nitrogen atom of the highly substituted pyrrolidine 30 was smoothly acylated through the intermediate formation of a mixed anhydride.
Cordero
Franca M
FM
Department of Organic Chemistry Ugo Schiff and HeteroBioLab, University of Florence, via della Lastruccia 13, 50019 Sesto Fiorentino (FI), Italy. franca.cordero@unifi.it
Salvati
Maria
M
Vurchio
Carolina
C
de Meijere
Armin
A
Brandi
Alberto
A
D000598:Amino Acids, Cyclic / Q000737:chemistry; D009842:Oligopeptides / Q000138:chemical synthesis; D011392:Proline / Q000031:analogs & derivatives* / Q000138:chemical synthesis; D011758:Pyrroles / Q000737:chemistry; D013237:Stereoisomerism
D000598:Amino Acids, Cyclic; D009842:Oligopeptides; D011758:Pyrroles; C013231:pyrroline; D011392:Proline; C010983:homoproline