Salts and prodrugs of 1-methyl-D-tryptophan

A method of treating cancer in a subject in need thereof, comprising administering a therapeutically effective amount of a compound of Formula 2:

• or a pharmaceutically acceptable salt thereof, wherein:
• R1 is —OH, —OC2-3alkyl, —OCH2CH(OH)CH2OH, —O(CH2)2N(CH3)2, —OC1-3alkyl-R3, —NHC(S)HR4(COOH), —NHC(R)HR4(COOH), —OC1-6alkylR6, —OC1-2alkyl-C(S)H(NH2)(COOH), or —OC1-2alkyl-C(R)H(NH2)(COOH);
• R2 is H, —C(O)C(S)H(NH2)R4, —C(O)C(R)H(NH2)R4, —C(O)CH2C(S)H(NH2), —C(O)OCH3, —C(O)OR5, or —C(O)NHR5;
• R3 is tetrahydropyran or
• R4 is H, —C1-5 alkyl, —(CH2)1-2SH, C1-5alkylSC1-5alkyl, C1-5alkylOC1-5 alkyl, —CH2—R6, —CH2OH, —CH(OH)CH3, —(CH2)1-2C(O)NH2, —(CH2)1-3C(O)OH, —(CH2)1-4NH2, or —(CH2)1-3NC(═NH2)NH2;
• C(S) and C(R) are carbons with the S or R stereochemistry, respectively, when R4 is not H;
• R5 is H, C1-6alkylR6, or R6;
• R6 is H, aryl, alkylaryl, heteroaryl, cycloalkyl, or heterocycloalkyl, wherein the aryl, alkylaryl, heteroaryl, cycloalkyl or heterocycloalkyl is optionally substituted with one, two or three R7 groups;
• each R7 is independently halogen, cyano, nitro, —OR, —N(R)2, —SR, —C(O)OR, C1-6alkyl, C1-6haloalkyl, —C(O)N(R)2, —C(O)R, —S(O)R, —S(O)OR, —S(O)N(R)2, —S(O)2R, —S(O)2OR, —S(O)2N(R)2, —OC(O)R, —OC(O)OR, —OC(O)N(R)2, —N(R)C(O)R, —N(R)C(O)OR, or —N(R)C(O)N(R)2, wherein R is H or C1-4alkyl;
• with the proviso that R1 cannot be OH when R2 is H, and the compound cannot be Nα-tert-butoxycarbonyl-1-methyl-D-tryptophan, ethyl Nα-benzyl-1-methyl-D-tryptophanate, or benzyl Nα-(tert-butoxycarbonyl)-1-methyl-D-tryptophanate;
• and
• wherein the cancer is selected from melanoma, colon cancer, lung cancer, or breast cancer.