Synthesis and structure-activity relationship (SAR) studies of L-cysteine-based N-type calcium channel blockers are described. In the course of exploring SAR of the N- and C-terminal substituents, the L-cysteine derivative 4b was found to be a potent N-type calcium channel blocker with an IC50 value of 0.14 muM on IMR-32 assay. Compound 4b showed 12-fold selectivity for N-type over L-type calcium channels on AtT-20 assay. (C) 2002 Elsevier Science Ltd. All rights reserved.
Total synthesis of (−)-eudistomins with an oxathiazepine ring. Part 1. Formation of the oxathiazepine ring system
Formation of the oxathiazepine ring in eudistomins 1 was investigated. Thiazolidinyl-β-carboline 5 was successfully transformed into thiaindoloquinolizidine 7, but attempted oxidative transformation of 7 to 1 was not successful. The oxidative cyclization of 1-substituted-2 hydroxy-β-carboline 24 with NCS or the acid-catalyzed cyclization of the corresponding S-oxide 26 with TsOH gave oxathiazepine
The optically active 1-amino-3-thiaindoloquinolizidine 8 was synthesized by rearrangement of the β-carboline 6 which was obtained by the Bischler-Napieralski reaction of the thioamide 4b followed by NaBH4 reduction, whereas the isomer 7 gave the pentacycle 9.