with regard to the srs-a leukotrienes , analogs differed from the native structures in the position of the peptide side chain and/or the hydroxyl group , the number and position of ethylenic bonds , the chirality at optically-active centers , or the structures of the four polar substituents in the c-1 to c-6 region .
C0038091
srs-a
C0023545
leukotrienes