Tryptamine prodrugs

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 C1-5 alkyl, or arylalkyl;
• (2) R4 is
• a. —X—CO2H, where X is a linear, cyclic or branched, saturated or unsaturated carbon chain (preferably C1-5 alkyl), optionally substituted with —OH or —CO2H, or an aromatic ring, optionally substituted with alkyl or CO2H;
• or
• b. (R9)(R10)N—, wherein R9 is X—CO2H, where X is defined as above, and R10 is hydrogen, linear or branched alkyl (preferably C1-5 alkyl) or arylalkyl, optionally substituted by —OH or —CO2H;
• (3) R5 is hydrogen, linear or branched alkyl (preferably C1-5 alkyl), arylalkyl, or O—R5′, where R5′ is hydrogen, linear or branched alkyl (preferably C1-5 alkyl);
• and
• (4) R7 and R8:
• a. are each independently selected from hydrogen, linear or branched alkyl (preferably C1-5 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.