TRYPTAMINE PRODRUGS

1 . A tryptamine or isotryptamine compound of Formula (I) (II), (III) or (IV) or a pharmaceutically acceptable salt or zwitterion thereof:

wherein:

(1) R1, R2, and R6 are each independently selected from hydrogen, linear or branched alkyl, preferably C 1-5 alkyl, or arylalkyl;

(2) R4 is

a. —X—CO 2 H, where X is a linear, cyclic or branched, saturated or unsaturated carbon chain (preferably C 1-5 alkyl), optionally substituted with —OH or —CO 2 H, or an aromatic ring, optionally substituted with alkyl or CO 2 H; or

b. (R9)(R10)N—, wherein R9 is X—CO 2 H, where X is defined as above, and R10 is hydrogen, linear or branched alkyl (preferably C 1-5 alkyl) or arylalkyl, optionally substituted by —OH or —CO 2 H;

(3) R5 is hydrogen, linear or branched alkyl (preferably C 1-5 alkyl), arylalkyl, or O—R5′, where R5′ is hydrogen, linear or branched alkyl (preferably C 1-5 alkyl); and

(4) R7 and R8:

a. are each independently selected from hydrogen, linear or branched alkyl (preferably C 1-5 alkyl), or arylalkyl, or

b. together form a non-aromatic N-containing heterocycle, optionally substituted with alkyl, preferably where the entire heterocyclic structure does not contain more than 12 atoms.

2 . The compound defined in claim 1 , selected from the group consisting of:

3 . The compound defined in claim 1 wherein:

(1) R1, R2, and R6 are each independently selected from H or linear C 1-5 alkyl;

(2) R4 is —X— CO 2 H, where X is a linear or branched C 1-5 carbon chain, optionally substituted with OH or CO 2 H;

(3) R5 is hydrogen, linear or branched C 1-5 alkyl, arylalkyl, or O—R5′, where R5′ is hydrogen, linear or branched C 1-5 alkyl; and/or

(4) R7 and R8 are each independently selected from H or linear or branched C 1-5 alkyl.

4 . The compound defined in claim 3 wherein R7 and R8 are the same or different, and are linear or branched C 1-4 alkyl.

5 . The compound defined in claim 4 where R7 and R8 are each methyl or isopropyl.

6 . The compound defined in claim 3 where X is a linear C1-C3 chain, optionally substituted with OH or CO2H.

7 . The compound defined in claim 5 wherein X is a linear C3 chain.

8 . The compound defined in claim 7 wherein R7 and R8 are both methyl, or R7 and R8 are both isopropyl, or one of R7 and R8 is methyl and the other is isopropyl.

9 . The compound defined in claim 1 , wherein at least one or more of hydrogen, carbon, nitrogen, oxygen, chlorine, or fluorine is replaced with 2 H, 3 H, 11 C, 13 C, 14 C, 13 N, 15 N, 17 O, 18 O, 36 Cl or 18 F, respectively.

10 . A composition comprising a compound defined in any one of claims 1-9 , and a pharmaceutically acceptable excipient.

11 . The composition defined in claim 10 comprising an oral dosage formulation or an injectable formulation.

12 . The composition defined in claim 11 which is a solution for injection.

13 . The composition defined in claim 12 wherein the solution has a pH of between about 3.0 and 7.0.

14 . A method of treating a mental disorder, comprising the step of administering an effective amount of a compound defined in claim 1 .

15 . The method defined in claim 14 wherein the mental disorder is depression.

16 . (canceled)

17 . A method of making a compound defined in claim 1 comprising reacting a tryptamine comprising hydroxytryptamine or hydroxyisotryptamine with a cyclic anhydride in a suitable anhydrous solvent.

18 . The method defined in claim 17 , wherein the solvent contains a base with pKa greater than 4 and less than about 9, and the resulting compound is isolated as a zwitterion.

19 . The method defined in claim 18 wherein the solvent is pyridine.

20 . The method defined in claim 19 wherein the compound is a compound defined in claim 2 .

21 . The method defined in claim 17 wherein the tryptamine is 4-OH diisopropyltryptamine or psilocin and the cyclic anhydride is succinic anhydride or glutaric anhydride.