(S)-3-[(Z)-isobutylidene]hexahydropyrrolo[1,2-a]pyrazine-1,4-dione

(3S,8aS)-6,7,8,8a-tetrahydro-1-methoxy-3-(2-methylpropyl)pyrrolo[1,2-a]pyrazin-4(3H)-one

L-Leu-L-Pro-OMe

Cbz-(L)-leucyl-(L)-prolyl benzotriazole

(S,S)-N-Boc-leucylproline methyl ester