N-substituted 5-(aminomethyl)-3, 3-diphenyl-2 (3H)-furanones, conformationally-constrained lactone relatives of benactyzine, was prepared. The compounds were examined in several paradigms that measure muscarinic (MI, M2, and M3) receptor antagonist activity. Selected members of the series that displayed potency and/or selectivity in these teats were studied for their effects on urinary bladder contraction, mydriasis, and salivation in guinea pigs. ...