A compound of Formulas,,,, or: or a salt thereof, wherein: R 1 is -OH or -OP 2; X 1 is CH 2 or O; X 2 is CH 2 or O; X 3 is CH 2 or O, provided that X 2 is O only if both X 1 and X 3 are each CH 2; R 2 is R 2a or R 2b; ----- represents either a single bond to R 2a or a double bond to R 2b; R 2a is -(CH 2) 3-6 CH 3, -(CH 2) 1-4 CH=CR x R x, -(CH 2) 1-4 CH=CR x (CH 2 CH 3), -CH=CH(CH 2) 1-3 C(R x) 3, -CH=CH(CH 2) 1-3 OCH 3, -(CH 2) 1-3 CH=CHCH=CR x R x, -CH=CH(CH 2) 1-3 CH=CR x R x, -CH=CHR z, -(CH 2) 1-3 R z, -(CH 2) 1-3 O(CH 2) 0-3 R z, -(CH 2) 1-3 S(CH 2) 0-3 R z, -CH 2 S R z, -CH 2 S 2 R z, -O(CH 2) 1-2 R z, -O(CH 2) 1-2 O(CH 2) 0-2 R z, -OC R z, -(CH 2) 1-4 O(CH 2) 0-9 C(R x) 3, -(CH 2) 1-4 O(CH 2) 0-9 CF 3, -(CH 2) 1-4 CR x R x O(CH 2) 0-4 C(R x) 3,-(CH 2) 1-3 O(CH 2) 1-4 CH=CR x (CH 2) 0-3 CH 3, -(CH 2) 1-3 O(CH 2) 1-4 CH=CR x R x, -(CH 2) 1-3 O(CH 2) 1-4 C R x R x, -(CH 2) 1-3 O(CH 2) 1-4 O(CH 2) 0-3 CH 3, -(CH 2) 1-3 S(CH 2) 0-4 C(R x) 3, -(CH 2) 0-3 O(CH 2) 1-4 S(CH 2) 0-3 C(R x) 3, -(CH 2) 1-3 S(CH 2) 1-4 Si(CH 3) 3, -(CH 2) 1-3 S (CH 2) 0-4 C(R x) 3, -(CH 2) 1-3 S 2 (CH 2) 0-4 C(R x) 3, -(CH 2) 1-5 NR x R x, -O(CH 2) 1-7 C(R x) 3, -O(CH 2) 1-4 O(CH 2) 0-4 C(R x) 3, -O(CH 2) 1-4 CH=CR x (CH 2) 0-3 CH 3, -O(CH 2) 1-4 O(CH 2) 0-3 C(R x) 3, -O(CH 2) 1-4 O(CH 2) 1-3 CH=CR x R x, -O(CH 2) 1-4 O(CH 2) 1-3 C≡CR x, -C (CH 2) 0-4 C(R x) 3, -OC (CH 2) 0-4 C(R x) 3, -OC CR x R x (CH 2) 0-4 C(R x) 3, -OC NR x (CH 2) 0-5 C(R x) 3,-NR x C NR x (CH 2) 0-5 C(R x) 3, -C(CH 3)=N-O(CH 2) 0-5 C(R x) 3, -C(CH 3)=N-O(CH 2) 1-2 (phenyl), -C(CH 3)=N-O(CH 2) 1-2 (fluorophenyl), -C(CH 3)=N-O(CH 2) 1-2 (methoxyphenyl), phenyl, or pyridinyl; R 2b is (i) a 6-membered spiro-ring having one oxygen atom and substituted with zero or 1 -(CH 2) 3 CH 3; or (ii) =N-O-(CH 2) 3 CH 3, =N-O-CH 2 CH(CH 3) 2, =N-OCH 2 CH 2 (phenyl), or =N-O-CH 2 CH 2 CH 2 (phenyl); R a is H or -OH; each R b is independently H or -CH 3; each R c is independently H, Cl, I, or -CH 3; each R x is independently H or -CH 3; and R z is phenyl, imidazolyl, pyrazolyl, pyridinyl, pyrimidinyl, pyrazinyl, quinolinyl, thiophenyl, thiazolyl, oxetanyl, C 3-6 cycloalkyl, adamantanyl, or tetrahydropyranyl, each substituted with zero to 4 substituents independently selected from F, Cl, I, C 1-4 alkyl, -O(C 1-3 -alkyl), -CF 3, -OCF 3, -(CH 2) 1-6 OCH 3, -CH 2 NR x R x, -C NR x R x, -C NR x (C 1-4 alkyl), and -CH 2 C NR x R x. with the provisos that (i) if said compound has the structure of Formula and R 2 is -(CH 2) 5 CH 3, then at least one of R b and R c is not H; and (ii) if said compound has the structure of Formula and X 1, X 2, and X 3 are each CH 2, then R 2a is not -(CH 2) 5 CH 3. R 1 is -OH or -OP 2; X 1 is CH 2 or O; X 2 is CH 2 or O; X 3 is CH 2 or O, provided that X 2 is O only if both X 1 and X 3 are each CH 2; R 2 is R 2a or R 2b; ----- represents either a single bond to R 2a or a double bond to R 2b; R 2a is -(CH 2) 3-6 CH 3, -(CH 2) 1-4 CH=CR x R x, -(CH 2) 1-4 CH=CR x (CH 2 CH 3), -CH=CH(CH 2) 1-3 C(R x) 3, -CH=CH(CH 2) 1-3 OCH 3, -(CH 2) 1-3 CH=CHCH=CR x R x, -CH=CH(CH 2) 1-3 CH=CR x R x, -CH=CHR z, -(CH 2) 1-3 R z, -(CH 2) 1-3 O(CH 2) 0-3 R z, -(CH 2) 1-3 S(CH 2) 0-3 R z, -CH 2 S R z, -CH 2 S 2 R z, -O(CH 2) 1-2 R z, -O(CH 2) 1-2 O(CH 2) 0-2 R z, -OC R z, -(CH 2) 1-4 O(CH 2) 0-9 C(R x) 3, -(CH 2) 1-4 O(CH 2) 0-9 CF 3, -(CH 2) 1-4 CR x R x O(CH 2) 0-4 C(R x) 3,-(CH 2) 1-3 O(CH 2) 1-4 CH=CR x (CH 2) 0-3 CH 3, -(CH 2) 1-3 O(CH 2) 1-4 CH=CR x R x, -(CH 2) 1-3 O(CH 2) 1-4 C R x R x, -(CH 2) 1-3 O(CH 2) 1-4 O(CH 2) 0-3 CH 3, -(CH 2) 1-3 S(CH 2) 0-4 C(R x) 3, -(CH 2) 0-3 O(CH 2) 1-4 S(CH 2) 0-3 C(R x) 3, -(CH 2) 1-3 S(CH 2) 1-4 Si(CH 3) 3, -(CH 2) 1-3 S (CH 2) 0-4 C(R x) 3, -(CH 2) 1-3 S 2 (CH 2) 0-4 C(R x) 3, -(CH 2) 1-5 NR x R x, -O(CH 2) 1-7 C(R x) 3, -O(CH 2) 1-4 O(CH 2) 0-4 C(R x) 3, -O(CH 2) 1-4 CH=CR x (CH 2) 0-3 CH 3, -O(CH 2) 1-4 O(CH 2) 0-3 C(R x) 3, -O(CH 2) 1-4 O(CH 2) 1-3 CH=CR x R x, -O(CH 2) 1-4 O(CH 2) 1-3 C≡CR x, -C (CH 2) 0-4 C(R x) 3, -OC (CH 2) 0-4 C(R x) 3, -OC CR x R x (CH 2) 0-4 C(R x) 3, -OC NR x (CH 2) 0-5 C(R x) 3,-NR x C NR x (CH 2) 0-5 C(R x) 3, -C(CH 3)=N-O(CH 2) 0-5 C(R x) 3, -C(CH 3)=N-O(CH 2) 1-2 (phenyl), -C(CH 3)=N-O(CH 2) 1-2 (fluorophenyl), -C(CH 3)=N-O(CH 2) 1-2 (methoxyphenyl), phenyl, or pyridinyl; R 2b is (i) a 6-membered spiro-ring having one oxygen atom and substituted with zero or 1 -(CH 2) 3 CH 3; or (ii) =N-O-(CH 2) 3 CH 3, =N-O-CH 2 CH(CH 3) 2, =N-OCH 2 CH 2 (phenyl), or =N-O-CH 2 CH 2 CH 2 (phenyl); (i) a 6-membered spiro-ring having one oxygen atom and substituted with zero or 1 -(CH 2) 3 CH 3; or (ii) =N-O-(CH 2) 3 CH 3, =N-O-CH 2 CH(CH 3) 2, =N-OCH 2 CH 2 (phenyl), or =N-O-CH 2 CH 2 CH 2 (phenyl); R a is H or -OH; each R b is independently H or -CH 3; each R c is independently H, Cl, I, or -CH 3; each R x is independently H or -CH 3; and R z is phenyl, imidazolyl, pyrazolyl, pyridinyl, pyrimidinyl, pyrazinyl, quinolinyl, thiophenyl, thiazolyl, oxetanyl, C 3-6 cycloalkyl, adamantanyl, or tetrahydropyranyl, each substituted with zero to 4 substituents independently selected from F, Cl, I, C 1-4 alkyl, -O(C 1-3 -alkyl), -CF 3, -OCF 3, -(CH 2) 1-6 OCH 3, -CH 2 NR x R x, -C NR x R x, -C NR x (C 1-4 alkyl), and -CH 2 C NR x R x. with the provisos that (i) if said compound has the structure of Formula and R 2 is -(CH 2) 5 CH 3, then at least one of R b and R c is not H; and (ii) if said compound has the structure of Formula and X 1, X 2, and X 3 are each CH 2, then R 2a is not -(CH 2) 5 CH 3.