Biodegradable lipids for the delivery of active agents

A compound of formula TB

• wherein
• R1 and R2 are each, independently, alkyl, alkenyl, or alkynyl;
• or
• R1 and R2, together with the nitrogen atom to which they are attached, form an optionally substituted heterocylic ring;
• each occurrence of R is, independently, —(CR3R4)—;
• each occurrence of R3 and R4 are, independently H or alkyl;
• a is 1, 2, 3, 4, 5 or 6;
• M1 and M2 are each, independently, selected from the group consisting of —C(O)O—, —OC(O)—, —OC(O)O—, —C(O)NH—, —C(O)S—, —C(S)O—, —CR5═NO—, —CR5═N—, and —O—Si(R6R6)O—, wherein each occurrence of R5 is, independently, H or alkyl, and R6 is H or C1-C6 alkyl;
• each of R9 and R10 are independently alkylene or alkenylene;
• and
• each of R11 and R12 are independently alkyl or alkenyl;
• with the proviso that:
• R9, M1, and R11 are together at least 8 carbons atoms in length;
• and
• R10, M2, and R12 are together at least 8 carbons atoms in length.

A compound of formula IC

• wherein
• R1 and R2 are each, independently, optionally substituted alkyl, alkenyl, or alkynyl;
• or
• R1 and R2, together with the nitrogen atom to which they are attached, form an optionally substituted heterocylic ring;
• each occurrence of R is, independently, —(CR3R4)—;
• each occurrence of R3 and R4 are, independently H or alkyl;
• a is 1, 2, 3, 4, 5 or 6;
• each of R9 and R10 are independently C12-C24 alkyl or alkenyl substituted at its terminus with a group M selected from the group consisting of —C(O)O—, —OC(O)—, —OC(O)O—, —C(O)NH—, —C(O)S—, —C(S)O—, —CR5═NO—, —CR5═N—, and —O—Si(R6R6)O—, wherein each occurrence of R5 is, independently, H or alkyl, and R6 is H or C1-C6 alkyl.

A compound selected from a compound of formulas II-XXIII:

• and salts thereof,
• wherein
• m, n, o and p are each, individually, 1-25, with the proviso that:
• (i) in Formulas (II), (IV), (VI) and (VII), m and p are both 4 or greater;
• (ii) in Formulas (VIII), (X), (XII), (XIV), (XVI), (XVIII), (XXI) and (XXIII), m is 4 or greater;
• and
• (iii) in Formulas (VIII), (IX), (XII) and (XIII), p is 8 or greater.