A compound represented by Structural Formula: or a pharmaceutically acceptable salt thereof, wherein: the enantiomeric excess or diastereomeric excess of the compound or pharmaceutically acceptable salt thereof is at least 90%; R is (C 1 -C 18)alkyl, (C 6 -C 18)aryl or (C 6 -C 18)aryl(C 1 -C 18)alkyl and is substituted with at least one acidic substituent selected from the group consisting of -CO 2 H, -SO 3 H, -PO 3 H 2, -OSO 3 H, -OPO 3 H 2, -B 2 and -NHOH, wherein the aryl of the (C 6 -C 18)aryl or (C 6 -C 18)aryl(C 1 -C 18)alkyl is optionally further substituted with one or more substituents selected from the group consisting of hydroxy, halo, (C 1 -C 3)alkyl, halo(C 1 -C 3)alkyl, cyano, nitro, (C 1 -C 3)alkoxy and thio(C 1 -C 3)alkyl; R' is hydrogen or (C 1 -C 18)alkyl, wherein (C 1 -C 18)alkyl is optionally substituted with one or more acidic substituents selected from the group consisting of -CO 2 H, -SO 3 H, -PO 3 H 2, -OSO 3 H, -OPO 3 H 2, -B 2 and -NHOH; and X is absent or is an amino acid, wherein the amino acid is aspartic acid, tyrosine, glutamic acid or alanine and is oriented to form an amide linkage with, provided that the compound of Structural Formula is not N - -lipoyl-glutamylalanine, N - -lipoyl-aminoethylphosphonic acid, or -5-(5-(1,2-dithiolan-3-yl)pentanamido)-2-hydroxybenzoic acid. the enantiomeric excess or diastereomeric excess of the compound or pharmaceutically acceptable salt thereof is at least 90%; R is (C 1 -C 18)alkyl, (C 6 -C 18)aryl or (C 6 -C 18)aryl(C 1 -C 18)alkyl and is substituted with at least one acidic substituent selected from the group consisting of -CO 2 H, -SO 3 H, -PO 3 H 2, -OSO 3 H, -OPO 3 H 2, -B 2 and -NHOH, wherein the aryl of the (C 6 -C 18)aryl or (C 6 -C 18)aryl(C 1 -C 18)alkyl is optionally further substituted with one or more substituents selected from the group consisting of hydroxy, halo, (C 1 -C 3)alkyl, halo(C 1 -C 3)alkyl, cyano, nitro, (C 1 -C 3)alkoxy and thio(C 1 -C 3)alkyl; R' is hydrogen or (C 1 -C 18)alkyl, wherein (C 1 -C 18)alkyl is optionally substituted with one or more acidic substituents selected from the group consisting of -CO 2 H, -SO 3 H, -PO 3 H 2, -OSO 3 H, -OPO 3 H 2, -B 2 and -NHOH; and X is absent or is an amino acid, wherein the amino acid is aspartic acid, tyrosine, glutamic acid or alanine and is oriented to form an amide linkage with, provided that the compound of Structural Formula is not N - -lipoyl-glutamylalanine, N - -lipoyl-aminoethylphosphonic acid, or -5-(5-(1,2-dithiolan-3-yl)pentanamido)-2-hydroxybenzoic acid. R is (C 1 -C 18)alkyl, (C 6 -C 18)aryl or (C 6 -C 18)aryl(C 1 -C 18)alkyl and is substituted with at least one acidic substituent selected from the group consisting of -CO 2 H, -SO 3 H, -PO 3 H 2, -OSO 3 H, -OPO 3 H 2, -B 2 and -NHOH, wherein the aryl of the (C 6 -C 18)aryl or (C 6 -C 18)aryl(C 1 -C 18)alkyl is optionally further substituted with one or more substituents selected from the group consisting of hydroxy, halo, (C 1 -C 3)alkyl, halo(C 1 -C 3)alkyl, cyano, nitro, (C 1 -C 3)alkoxy and thio(C 1 -C 3)alkyl; R' is hydrogen or (C 1 -C 18)alkyl, wherein (C 1 -C 18)alkyl is optionally substituted with one or more acidic substituents selected from the group consisting of -CO 2 H, -SO 3 H, -PO 3 H 2, -OSO 3 H, -OPO 3 H 2, -B 2 and -NHOH; and X is absent or is an amino acid, wherein the amino acid is aspartic acid, tyrosine, glutamic acid or alanine and is oriented to form an amide linkage with, provided that the compound of Structural Formula is not N - -lipoyl-glutamylalanine, N - -lipoyl-aminoethylphosphonic acid, or -5-(5-(1,2-dithiolan-3-yl)pentanamido)-2-hydroxybenzoic acid.