Scaffold hopping, synthesis and structure-activity relationships of 5,6-diaryl-pyrazine-2-amide derivatives: a novel series of CB1 receptor antagonists.

A scaffold hopping approach has been exploited to design a novel class of cannabinoid (CB1) receptor antagonists for the treatment of obesity. On the basis of shape-complementarity and synthetic feasibility the central fragment, a methylpyrazole, in Rimonabant was replaced by a pyrazine. The synthesis and CB1 antagonistic activities of a new series of 5,6-diaryl-pyrazine-2-amide derivatives are described. Several compounds showed antagonist potency below 10nM for the CB1 receptor.

Synthesis of XylbetaCer, Galbeta1-4XylbetaCer, NeuAcalpha2-3Galbeta1-4XylbetaCer and the Corresponding Lactone and Lactam Trisaccharides.

2-(Trimethylsilyl)ethyl 2-O-benzoyl- and 2,3-di-O-acetyl-beta-D-xylopyranosides (12 and 14) were synthesized in high yields and subjected to glycosylation with various glycosyl donors. Galactosylation of 12 gave the xylose analogue of TMSEt lactoside (3), which was transformed into the glycosyl acceptor 19. Sialylation then gave the xylose analogue of G(M3) trisaccharide (5). The TMSEt glycosides 10, 25, and 32 were transformed into the corresponding trichloroacetimidates, which were used for glycosylation of an azidosphingosine derivative. The resulting sphingosyl glycosides were transformed into the title ceramides. Treatment of NeuAcalpha2-3Galbeta1-4XylbetaCer (5) with acetic acid gave the corresponding 1"-->2'-lactone 7. Glycosylation of 12 or 14 with a G(M4)-lactam donor (40) gave the xylose analogue of G(M3)-lactam (42). There was a 3-fold increase in the formation of GAG chains in the presence of 0.5 &mgr;M XylbetaCer (2) in the medium.