This invention provides compounds and methods for treating melanocortin receptor associated disorders, such as weight loss disorders including cachexia resulting from cancer and other chronic illnesses. The compounds are represented by formula I:
wherein X is oxygen or sulfur; G is G1 or G2:
L
1
, L
2
, L
3
and Q are linker groups, and Rings A, B and C, and R
1
-R
14
are described in the specification. The compounds are antagonists of melanocortin receptors.
It was found that the dilithium salt (5), which was lithiated at the side-chain of 2-methyl-3-thiophenecarboxylic acid (4), was produced regioselectively by the reaction of 4 with lithium diisopropylamide (LDA). The reactions of 5 with alkyl halides resulted in the formation of 2-alkyl-3-thiophenecarboxylic acids (7). Further, δ-lactone derivatives (11) were obtained by the cyclization of the adducts (10) which were produced from 5 with aldehydes and ketones.