Synthesis and cholinergic affinity of diastereomeric and enantiomeric isomers of 1-methyl-2-(2-methyl-1,3-dioxolan-4-yl)- pyrrolidine, 1-methyl-2-(2-methyl-1,3-oxathiolan-5-yl)pyrrolidine and of Their iodomethylates

Muscarinic antagonists with multiple stereocenters: Synthesis, affinity profile and functional activity of isomeric 1-methyl-2-(2,2-alkylaryl-1,3-oxathiolan-5-yl)pyrrolidine sulfoxide derivatives

Completing a long-lasting research on 1,3-oxathiolane muscarinic ligands, we have synthesized a set of isomeric 1-methyl-2-(2,2-alkylaryl-1,3-oxathiolan-5-yl)pyrrolidine 3-sulfoxide derivatives, containing three or four stereogenic centers. In general the compounds are very potent antagonists even if, unlike the corresponding agonists, they show modest subtype selectivity.

Synthesis and alpha4beta2 nicotinic affinity of unichiral 5-(2-pyrrolidinyl)oxazolidinones and 2-(2-pyrrolidinyl)benzodioxanes

The RS and SR enantiomers of 2-oxazolidinone and 1,4-benzodioxane bearing a 2-pyrrolidinyl substituent at the 5- and 2-position, respectively, were synthesized as candidate nicotinoids. One of the two benzodioxane stereoisomers reasonably fits the pharmacophore elements of (S)-nicotine and binds at alpha4beta2 nicotinic acetylcholine receptor with submicromolar affinity. Interestingly, both the synthesized pyrrolidinylbenzodioxanes exhibit analogous affinity at alpha(2) adrenergic receptor resembling the behaviour of some known alpha(2)-AR ligands recently proved to possess neuronal nicotinic affinity.

Synthesis and stereoselective functionalization of silylated heterocycles as a new class of formyl anion equivalents

The fluoride ion-induced reactivity of a series of silyl heterocycles leads to the generation of nucleophilic species capable of interacting with electrophiles, thus disclosing new classes of formyl and acyl anion synthons. Moreover, when reacting stereodefined molecules, the stereoinformation of the reacting carbon-silicon bond is transferred to the newly formed carbon-carbon bond, suggesting possible applications in stereoselective synthesis. Thus, silyl dithiolanes, oxathiolanes, dioxolanes, thiazolidines and oxazolidines can be efficiently and stereoselectively functionalized under fluoride ion conditions in the presence of electrophiles. While direct access to silyl heterocycles is generally either prevented or troublesome, a novel protocol for their synthesis has also been developed, together with a simple general access route to several functionalized and stereodefined mercaptans, building blocks for the construction of silyl heterocycles.

Muscarinic subtype affinity and functional activity profile of 1-methyl-2-(2-methyl-1,3-dioxolan-4-yl)pyrrolidine and 1-methyl-2-(2-methyl-1,3-oxathiolan-5-yl)pyrrolidine derivatives

Starting from two previously studied muscarinic full agonists, characterized by a 1,3-dioxolane ((+)-1) and a 1,3-oxathiolane ((+)-2) cycle, two new series of muscarinic ligands were designed, obtained by the steric complication of the parent compounds produced by freezing the aminoalkyl chain into a pyrrolidine ring. Both tertiary amines and the corresponding iodomethyl derivatives were synthesised and studied, and several compounds of the series which behaved as muscarinic agonists have been selected, on the basis of preliminary binding experiments on rat cortex homogenates, for the present work. Results are presented obtained from testing the affinity of the selected compounds against cloned human muscarinic receptors expressed in CHO cells, in order to evaluate subtype selectivity. Their functional activity on classical models of M1-M4 receptors, in guinea pig and rabbit tissues is also reported. With respect to parent compounds, the new molecules present some selectivity toward hm2 receptors; fair M2 selectivity is also evident in functional studies, where these compounds behave as partial agonists. Among the other compounds of the series (2S, 4'R, 2'S)-1,1-dimethyl-2-(2-methyl-1,3-dioxolan-4-yl)pyrrolidinium iodide (-)-3 and (2R, 5'S, 2'S)-1-methyl-2-(2-methyl-1,3-oxathiolan-5-yl)pyrrolidine (+)-5 present a promising pharmacological profile. Compound (-)-3 shows modest hm2 selectivity in binding experiments but a clearcut M2 selectivity in functional tests, where it behaves as a weak antagonist on M1 and M4 subtypes, as a weak full agonist on the M3 subtype and as a potent partial agonist on M2 subtype. Tertiary amine (+)-5 presents a quite similar profile but appears more interesting since, lacking a permanent charge on the nitrogen atom, it may represent an interesting tool to study CNS muscarinic receptors. Our results confirm that sterical complication of parent compounds (+)-1 and (+)-2 produces more selective muscarinic agonists.