Communications to the Editor
J ournal of Medicinal Chemistry, 1998, Vol. 41, No. 22 4185
A.; Newberry, N.; Salamome, J . D.; Hirshfield, J .; Springer, J .
P. Synthesis and characterization of all four isomers of the
muscarinic agonist 2′-methylspiro[1-azabicyclo[2.2.2]octane-3,4′-
[1,3]dioxolane]. J . Med. Chem. 1987, 30, 969-975.
carboxylic acid and aliphatic and aromatic hydroxyl probe
groups. The resulting interaction maps obtained by GRID were
consistent with the electrostatic potential maps and provided
the pertinent information for construction of a pseudoreceptor
site model.
(7) (a) Wu, E. S. C.; Griffith, R.; Kover, A.; Loch, J . T., III; Mullen,
G.; Murray, R. J .; Blosser, J . C.; Machulskis, A. C.; McCreedy,
S. A. In Vitro Muscarinic Activity of Novel Spiromuscarones and
Related Analogues. J . Med. Chem. 1995, 38, 1558-1570. (b)
Tsukamoto, S.; Fujii, M.; Yasunaga, T.; Matsuda, K.; Wanibuchi,
F.; Hidaka, K.; Furuya, T.; Tamura, T. Synthesis and structure-
activity studies of a series of 1-oxa-8-azaspiro[4.5]decanes as M1
muscarinic agonists. Bull. Chem. Pharm. 1995, 43, 842-52. (c)
Wu, E. S. C.; Mack, R. A.; Kover, A.; Loch, J . T., III; Mullen, G.;
Murray, R. J .; Gordon, J .; Machulskis, A. C.; McCreedy, S. A.;
Blosser, J . C. Synthesis and Biological Activity of Enantiomers
of a Conformationally Restricted Muscarone Analogue. Bioorg.
Med. Chem. Lett. 1995, 5, 1813-1818.
(8) (a) Street, L. J .; Baker, R.; Book, T.; Kneen, C. O.; MacLeod, A.
M.; Merchant, K. J .; Showell, G. A.; Saunders, J .; Herbert, R.
H.; Freedman, S. B.; Harley, E. A. Synthesis and biological
activity of 1,2,4-oxadiazole derivatives: highly potent and ef-
ficacious agonists for cortical muscarinic receptors. J . Med.
Chem. 1990, 35, 2690-2697. (b) Freedman, S. B.; Haley, E. A.;
Patel, S.; Newberry, N. R.; Gilbert, M. J .; McKnight, A. T.; Tang,
J . K.; Maguire, J . J .; Mudunkotuwa, N. T.; Baker, R.; Street, L.
J .; MacLeod, A. M.; Saunders, J .; Iversen, L. L. A novel series
of nonquaternary oxadiazoles acting as full agonists at musca-
rinic receptors. Br. J . Pharmacol. 1990, 101, 575-580.
(12) The cell constants were determined from a least-squares fit of
the setting angles for 25 accurately centered reflections. X-ray
intensity data were collected on an Enraf-Nonius CAD4 diffrac-
tometer employing graphite-monochromated Cu KR radiation
(λ ) 1.541 84 Å) and using the ω-2θ scan technique. A total of
2485 reflections were measured over the ranges: 4° e 2θ e 130°,
-16 e h e 16, 0 e k e 9, 0 e l e 13. Three standard reflections
measured every 3500 s of X-ray exposure showed no intensity
decay over the course of data collection. The intensity data were
corrected for Lorentz and polarization effects but not for absorp-
tion. Of the reflections measured,
a total of 1715 unique
reflections with F2 > 3σ(F2) were used during subsequent
structure refinement. The structure was solved by direct meth-
ods (SIR88). Refinement was by full-matrix least squares
technique based on F to minimize the quantity ∑w(|Fo| - |Fc|)2
with ω ) l/σ2(F). Non-hydrogen atoms were refined anisotropi-
cally, and hydrogen atoms were refined isotropically. Refinement
converged to R1 ) 0.052 and R2 ) 0.075.
(13) Cramer, R. D., III; Patterson, D. E.; Bunce, J . E. Comparative
Molecular Field Analysis (CoMFA). 1. Effect of shape on binding
of steroids to carrier proteins. J . Med. Chem. 1988, 31, 5959-
5967.
(14) Wu, E. S. C.; Kover, A.; Loch, J . T., III; Rosenberg, L. P.; Semus,
S. F.; Verhoest, P. R.; Gordon, J . C.; Machulskis, A. C.; Mc-
Creedy, S. A.; Zongrone, J .; Blosser, J . C. Acylhydrazones as M1/
M3 selective muscarinic agonists. Bioorg. Med. Chem. Lett. 1996,
6, 2525-2530.
(15) Kellogg, G. E.; Semus, S. F.; Abraham, D. J . HINT: a new
method of empirical hydrophobic field calculation for CoMFA.
J . Comput. Aided Mol. Des. 1991, 5, 545-552.
(9) The overall yield, starting from the ketone 2, of the fumarate
salt of pure 1a (the syn isomer) which was isolated and purified
from a mixture of syn and anti isomers of 1 was 6%.
(10) (a) Tecle, H.; Lauffer, D. J .; Mirzadegan, T.; Moos, W. H.;
Moorland, D. W.; Pavia, M. R.; Scharwz, R. D.; Davis, R. E.
Synthesis and SAR of bulky 1-azabicyclo[2.2.1]-3-one oximes as
muscarinic receptor subtype selective agonists. Life Sci. 1992,
52, 505. (b) Tecle, H.; Lauffer, D. J .; Mirzadegan, T.; Moos, W.
H.; Moorland, D. W.; Pavia, M. R.; Scharwz, R. D.; Davis, R. E.
A rationale for the design and synthesis of m1 selective mus-
carinic agonists. Bioorg. Med. Chem. Lett. 1992, 2, 821. (c) Moos,
W. H.; Bergmeier, S. C.; Coughenour, L. L.; Davis, R. E.;
Hershenson, F. M.; Kester, J . A.; McKee, J . S.; Marriott, J . G.;
Scharwz, R. D.; Tecle, H.; Thomas, A. J . Cholinergic Agent:
Effect of methyl substitution in a series of arecoline derivatives
on building to muscarinic acetylcholine receptors. J . Pharm. Sci.
1992, 81, 1015-1019.
(16) Fraser, C. M.; Wang, C.-D.; Robinson, D. A.; Gocayne, J .; Venter,
J . C. Site-Directed Mutagenesis of m1 Muscarinic Acetylcholine
Receptors: Conserved Aspartic Acids Play Importance Roles in
Receptor Function. Mol. Pharmacol. 1989, 36, 840-847.
(17) Wess, J .; Gdula, D.; Brann, M. R. Site-directed Mutagenesis of
m3 Muscarinic Receptors: Identification of Threonine and
Tyrosine Residues Involved in Agonist but not Antagonist
Binding. EMBO J . 1991, 10, 3729-3734.
(18) The detailed report of this compound will be published elsewhere.
Inhibition in cAMP was 100% as compared with that of
carbachol.7a
(11) Compound 1a was constructed in the protonated form, from the
X-ray crystallographic data12 (Figure 1), using the Sybyl suite
of programs, version 6.3, Tripos Associates, St. Louis, MO.
Geometry optimization was performed initially with the Tripos
force field, followed by the 3-21G* Hamiltonian as implemented
within Spartan, Wavefunction, Irvine, Ca. Atomic charges were
calculated via natural population analysis and fitted to the
electrostatic potential over the surface density. Potential energy
isosurfaces were contoured to identify the maximal regions of
electrostatic attraction and repulsion from the proton probe. The
attractive areas were concentrated around the carbonyl and ring
ether oxygens, along the vectors of their respective lone pairs.
The molecular environment was subsequently sampled by an
assortment of probe atoms and groups using GRID, Molecular
Diversity Limited, Oxford, England, to identify potential interac-
tion sites. Primary interaction domains were examined with
(19) Carroll, P. J .; De Amici, M.; De Micheli, C.; Toma, L. Confor-
mational Studies of Muscarone Analogues: X-ray Analysis and
Molecular Mechanics Calculations. J . Med. Chem. 1992, 35,
305-309.
(20) Chiou, C. Y.; Long, J . P.; Cannon, J . G.; Armstrong, P. D. The
cholinergic effects and rates of hydrolysis of conformationally
rigid analogues of acetylcholine. J . Pharmacol. Exp. Ther. 1969,
166, 243-248.
(21) Waser, P. G. Chemistry and pharmacology of muscarinie,
muscarone, and some related compounds. Pharmacol. Rev. 1961,
13, 465-515.
(22) Casy, A. F. In Progress in Medicinal Chemistry; Ellis, G. P., West,
G. B., Eds.; North-Holland Publishing: New York, 1975; Vol.
11, Chapter 1, pp 1-65.
J M980192X