The synthetic peptide, R2N-COCH2OCH 2CO-Gly-Gly-Gly-PrO-Gly-Gly-Gly-OR′, was shown to be selective for Cl- over K+ when R is n-octadecyl and R′ is benzyl. Nineteen heptapeptides have now been prepared in which the N-terminal and C-terminal residues have been varied. All of the N-terminal residues are dialkyl but the C-terminal chains are esters, 2° amides, or 3° amides. The compounds having varied N-terminal anchors and C-terminal benzyl groups are as follows: 1, R = n-propyl; 2, R = n-hexyl; 3, R = n-octyl; 4, R = n-decyl; 5, R = n-dodecyl; 6, R = n-tetradecyl; 7, R = n-hexadecyl; 8, R = n-octadecyl. Compounds 9-19 have R = n-octadecyl and C-terminal residues as follows: 9, OR′ = OCH2CH3; 10, OR′ = OCH(CH 3)2; 11, OR′ = O(CH2)6CH 3; 12, OR′ = OCH2-c-C6H11; 13, OR′ = O(CH2)9CH3; 14, OR′ = O(CH2)17CH3; 15, NR′2 = N[(CH2)6CH3]2; 16, NHR′ = NH(CH2)9CH3; 17, NR′2 = N[(CH2)9CH3]2; 18, NHR′ = NH(CH2)17CH3; 19, NR′2 = N[(CH2)17CH3]2. The highest anion transport activities were observed as follows. For the benzyl esters whose N-terminal residues were varied, i.e. 1-8, compound 3 was most active. For the C18 anchored esters 10-14, n-heptyl ester 11 was most active. For the C18 anchored, C-terminal amides 15-19, di-n-decylamide 17 was most active. It was concluded that both the C-and N-terminal anchors were important for channel function in the bilayer but that activity was lost unless only one of the two anchoring groups was dominant.