A compound, or a pharmaceutically acceptable salt thereof, of formula: wherein: L 1 is a direct bond or C 1 -C 5 alkylene; E 1 is selected from -O-, -OC O-, -OC -δ 1, -OC N -δ 1, -OC S-δ 1, -N C -δ 1, -N C O-δ 1, -C O-δ 1, and -C N -δ 1; Q is H or C 1 -C 5 alkyl; δ 1 designates the bond linked to the R 1 group; R 1 is selected from: and wherein: R 4 and R 5 are each independently selected from group consisting of C 1 -C 6 alkyl, C 2 -C 6 alkenyl and C 2 -C 6 alkynyl; alternatively R 4 and R 5 may join to form 4-6 membered heterocyclic ring containing oxygen or up to 2 nitrogen, optionally substituted with 1 or 2 substituents each independently selected from a C 1 -C 6 alkyl, cyclopropyl, OH, and a C 1 -C 3 alkoxy group; R 6 is selected from C 1 -C 6 alkyl, C 2 -C 6 alkenyl, C 2 -C 6 alkynyl, C 3 -C 6 cycloalkyl and a 2-hydroxyethyl group; R 7 is selected from H, C 1 -C 6 alkyl, C 2 -C 6 alkenyl, and a C 2 -C 6 alkynyl group; a and c' are independently 1, 2, 3, 4, or 5; b, c and e are independently 0,1, or 2; d is 1, or 2; R 2 is selected from H, C 1 -C 12 alkyl, C 2 -C 12 alkenyl, C 2 -C 12 alkynyl, and L 2 is a direct bond or δ 2 -(CR 8 R 8') k -δ 3 wherein R 8 and R 8' are each independently H, C 1 -C 12 alkyl, C 2 -C 12 alkenyl or C 2 -C 12 alkynyl; δ 2 designates the bond linked to E 2 group, and δ 3 designates the bond linked to cyclopentyl scaffold described in formula; k is 1, 2, 3, 4, or 5; E 2 is selected from -O-, -OC O-, -OC -δ 4, -OC N -δ 4, -N C -δ 4,-N C O-δ 4, -C N -δ 4 or-C O-δ 4; Q is H or C 1 -C 5 alkyl; where δ 4 designates the bond linked to R 3 group; R 3 is selected from C 8 -C 20 alkyl, C 8 -C 20 alkenyl, C 8 -C 20 alkynyl, wherein: f is 0, or 1; g is 1, or 2; g' is 1, 2, 3, 4, or 5; h is 0, 1, 2, 3 or 4; R 9 is a C 6 -C 20 chain having the formula -(CH 2) i -[L 4 -(CH 2)] j -R 12, wherein: L 4 is selected from i is an integer in the range 6-20; j is 0, 1, 2, or 3; R 12 is selected from H and C 4 -C 8 alkyl; R 9' is selected from H, C 4 -C 10 alkyl, C 4 -C 10 alkenyl, and C 4 -C 10 alkynyl; R 10 and R 10' are each, independently selected from C 4 -C 10 alkyl, C 4 -C 10 alkenyl, and C 4 -C 10 alkynyl; L 3 is -OC -δ 5, -O-δ 5, or a direct bond; δ 5 designates the bond linked to R 10 and R 10'; and R 11 = R 9, or has the formula: L 1 is a direct bond or C 1 -C 5 alkylene; E 1 is selected from -O-, -OC O-, -OC -δ 1, -OC N -δ 1, -OC S-δ 1, -N C -δ 1, -N C O-δ 1, -C O-δ 1, and -C N -δ 1; Q is H or C 1 -C 5 alkyl; δ 1 designates the bond linked to the R 1 group; R 1 is selected from: and wherein: R 4 and R 5 are each independently selected from group consisting of C 1 -C 6 alkyl, C 2 -C 6 alkenyl and C 2 -C 6 alkynyl; alternatively R 4 and R 5 may join to form 4-6 membered heterocyclic ring containing oxygen or up to 2 nitrogen, optionally substituted with 1 or 2 substituents each independently selected from a C 1 -C 6 alkyl, cyclopropyl, OH, and a C 1 -C 3 alkoxy group; R 6 is selected from C 1 -C 6 alkyl, C 2 -C 6 alkenyl, C 2 -C 6 alkynyl, C 3 -C 6 cycloalkyl and a 2-hydroxyethyl group; R 7 is selected from H, C 1 -C 6 alkyl, C 2 -C 6 alkenyl, and a C 2 -C 6 alkynyl group; a and c' are independently 1, 2, 3, 4, or 5; b, c and e are independently 0,1, or 2; d is 1, or 2; R 2 is selected from H, C 1 -C 12 alkyl, C 2 -C 12 alkenyl, C 2 -C 12 alkynyl, and L 2 is a direct bond or δ 2 -(CR 8 R 8') k -δ 3 wherein R 8 and R 8' are each independently H, C 1 -C 12 alkyl, C 2 -C 12 alkenyl or C 2 -C 12 alkynyl; δ 2 designates the bond linked to E 2 group, and δ 3 designates the bond linked to cyclopentyl scaffold described in formula; k is 1, 2, 3, 4, or 5; E 2 is selected from -O-, -OC O-, -OC -δ 4, -OC N -δ 4, -N C -δ 4,-N C O-δ 4, -C N -δ 4 or-C O-δ 4; Q is H or C 1 -C 5 alkyl; where δ 4 designates the bond linked to R 3 group; R 3 is selected from C 8 -C 20 alkyl, C 8 -C 20 alkenyl, C 8 -C 20 alkynyl, wherein: f is 0, or 1; g is 1, or 2; g' is 1, 2, 3, 4, or 5; h is 0, 1, 2, 3 or 4; R 9 is a C 6 -C 20 chain having the formula -(CH 2) i -[L 4 -(CH 2)] j -R 12, wherein: L 4 is selected from i is an integer in the range 6-20; j is 0, 1, 2, or 3; R 12 is selected from H and C 4 -C 8 alkyl; R 9' is selected from H, C 4 -C 10 alkyl, C 4 -C 10 alkenyl, and C 4 -C 10 alkynyl; R 10 and R 10' are each, independently selected from C 4 -C 10 alkyl, C 4 -C 10 alkenyl, and C 4 -C 10 alkynyl; L 3 is -OC -δ 5, -O-δ 5, or a direct bond; δ 5 designates the bond linked to R 10 and R 10'; and R 11 = R 9, or has the formula: