Forskolin carbamates: binding and activation studies with type I adenylyl cyclase.
Three series of analogs were regioselectively prepared from a protected forskolin precursor to afford 7-carbamoyl-7-desacetylforskolins (series 1), 6-carbamoyl-7-desacetylforskolins (series 2), and 6-carbamoylforskolins (series 3). The analogs were pharmacologically evaluated for binding (IC50) to and activation (EC50) of type I adenylyl cyclase in membranes from stably transfected Sf9 cell lines expressing a single adenylate cyclase subtype. The following ranges were determined for the IC50's and EC50's of each individual series: series 1, IC50 = 43-1600 nM, EC50 = 0.5-9.6 microM; series 2, IC50 = 65-680 nM, EC50 = 0.63-6.5 microM; series 3, IC50 = 21-271 nM, EC50 = 0.5-8.1 microM (forskolin IC50 = 41 nM and EC50 = 0.5 microM). Activation paralleled binding; however, some analogs exhibited poor binding and good activation whereas others demonstrated good binding but poor activation. Steric bulk tended to diminish binding and activation when at the 6- or 7-position, although bulk was accommodated at the 6-position if the 7-site was reacetylated. Acylation of the 7-position by the carbamoyl linker or acetyl was important for obtaining good binding and activation; however, the effect was more pronounced with binding. For both binding and activation, small, linear, lipophilic substituents (propyl, allyl, isopropyl) are well tolerated at the 7-position but less so in the 6-position, even when the 7-site is reacetylated. Planar aromatic moieties (phenyl and 2-pyridinyl) demonstrated moderate to good potency for binding and activation when located at either the 6- or 7-positions. There is an overall trend toward increasing potency for both binding and activation with polar substituents.
Robbins
J D
JD
Center for Biologics Evaluation and Research, Laboratory of Chemical Biology, Food and Drug Administration, Bethesda, Maryland 20892, USA.
Boring
D L
DL
Tang
W J
WJ
Shank
R
R
Seamon
K B
KB
D000262:Adenylyl Cyclases / Q000187:drug effects* / Q000235:genetics / Q000378:metabolism; D000818:Animals; D002219:Carbamates / Q000138:chemical synthesis* / Q000494:pharmacology; D002460:Cell Line; D005576:Colforsin / Q000031:analogs & derivatives* / Q000494:pharmacology; D004789:Enzyme Activation; D018411:Spodoptera
D002219:Carbamates; D005576:Colforsin; D000262:Adenylyl Cyclases