Synthesis and Bioactivity of Propranolol Analogues with a Rigid Skeleton. I

The synthesis of two kinds of propranolol analogues, A and B, with a rigid skeleton was investigated. The compounds were designed to help identify the conformation involved in β-adrenergic receptor-propranolol interaction. The key intermediate, 2-hydroxy·2, 3-dihydronaphtho[1, 8-bc]pyran (5), was obtained starting from acenaphthenone (1). On sequential dehydration, hydroboration, and oxidation, 5 gave 2, 3-dihydronaphtho[1, 8-bc]pyran-3-one (8), which was converted to compound A. Compound 5 was also derived to 2-formyl-2, 3-dihydronaphtho[1, 8-bc]pyran (13) via the 2-vinyl compound (12). Condensation of nitromethane with 13 followed by reduction and alkylation produced the desired compound B. The β-blocking activities of A and B were examined.