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

Bioorganic & Medicinal Chemistry 11 (2003) 3153–3164

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^y

Silvia Dei,^aCristina Bellucci,^aMichela Buccioni,^bMarta Ferraroni,^cFulvio Gualtieri,^a,*

Luca Guandalini,^aDina Manetti,^aRosanna Matucci,^dMaria Novella Romanelli,^a

Serena Scapecchi^aand Elisabetta Teodori^a

a

`

Dipartimento di Scienze Farmaceutiche, Universita di Firenze, Via Gino Capponi 9, 50121 Firenze, Italy

b

`

Dipartimento di Chimica, Universita di Camerino,Via S.Agostino 1, 62032 Camerino (MC), Italy

`

Dipartimento di Farmacologia Preclinica e Clinica, Universita di Firenze, Viale Pieraccini 6, 50139 Firenze, Italy

c

Dipartimento di Chimica, Universita di Firenze, Via della Lastruccia 5, 50019 Sesto Fiorentino (FI), Italy

d

Received 3December 2002; accepted 4 April 2003

Abstract—Four out of the eight possible stereoisomers of 1-methyl-2-(2-methyl-1,3-dioxolan-4-yl)pyrrolidine, 1-methyl-2-(2-

methyl-1,3-oxathiolan-5-yl)pyrrolidine and the corresponding iodomethylates have been synthesised. They were formally derived

from hybridisation of potent though unselective agonists studied before, such as 1,3-dioxolane 1 and 1,3-oxathiolane 2, with the

structure of nicotine. It was expected that, by exalting the molecular complexity of the parent compounds, in particular through

stereochemical complication in the proximity of the critical cationic head of the molecule, the chance to ﬁnd agonists able to dis-

criminate among cholinergic receptors subtypes would increase. The relative and absolute conﬁguration of the compounds obtained

has been established by means of NMR spectroscopy and X-ray crystallography. In preliminary studies, their binding aﬃnity has

been evaluated on rat brain nicotinic and muscarinic receptors. While none of the compounds showed any nicotinic aﬃnity up to

the dose of 10 mM, most of the iodomethylates were endowed with promising aﬃnity for the muscarinic receptors.

Introduction

Alzheimer’s disease,³and generally those of the central

nervous system. The cholinergic hypothesis of Alz-

heimer’s disease⁴has stimulated the synthesis and the

pharmacological evaluation of hundreds of new com-

pounds, most of them agonists or able to restore the

central cholinergic tone. Initially, the research almost

exclusively regarded muscarinic agonists⁵and several

compounds were proposed for pre-clinical and clinical

studies. However, clinical results were rather dis-

appointing, mainly because of problems with toxicity

attributed to poor selectivity against the M₁muscarinic

receptor subtype. Later on, the research seemed to have

shifted toward the synthesis and the study of agonists of

the nicotinic receptors⁶that appear to play a major role

in the CNS, mainly by regulating the release of several

important neurotransmitters. In both cases, the poor

selectivity of the molecules studied has always repre-

sented the major problem. The possibility of using

Cholinergic compounds have been studied widely in the

past decades, to identify molecules useful for further

characterisation of muscarinic¹and nicotinic²receptor

subtypes. However, while characterisation through

antagonists has progressed satisfactorily, there are at

present no agonists that are able to discriminate mus-

carinic or nicotinic subtypes. Thus, new agonists selec-

tive for one of the several muscarinic and nicotinic

receptor subtypes would be extremely useful not only to

further characterise the receptors but also for their

therapeutic potential in neurodegenerative diseases like

^ySupplementary data associated with this article can be found at doi:

10.1016/S0968-0896(03)00236-0

*Corresponding author. Tel.: +39-055-375-7295; fax: +39-055-

240776; e-mail: fulvio.gualtieri@uniﬁ.it

doi:10.1016/S0968-0896(03)00236-0

3154

S. Dei et al. / Bioorg. Med. Chem. 11 (2003) 3153–3164

agonists with a dual action (nicotinic and muscarinic),

as indeed happens for the natural mediator acetyl-

choline, seems to have been overlooked so far. Perhaps

the reason lies in the diﬃculty of identifying compounds

that are, at the same time, selective for muscarinic M₁

and nicotinic a2b4 or a7 receptors, which are the sub-

types mainly involved in neurodegenerative diseases.⁷

out of the four possible diastereoisomers were obtained

in reasonable yields, the other two being present only in

traces which, so far, prevented their sound charac-

terisation. Very luckily, the two isolated stereoisomers,

both in the 1,3-dioxolane and 1,3-oxathiolane series,

present a cis geometry of the side chains, that is iden-

tical to that of the most potent isomers of the parent

compounds 1 and 2. The situation parallels that of the

parent compounds 1 and 2 for which the cis isomers are

prevalent with respect to the trans ones (3:2¹³and 4:1,¹²

respectively).

For several years, we have been working with cholinergic

agonists, characterised by a pentatomic cycle, among

them 1,3-dioxolanes and 1,3-oxathiolanes.⁸Iodomethy-

lates of both series such as 1 and 2 (Chart 1), show high

agonistic activity on muscarinic as well as on nicotinic

receptors.^9À12However, both series of compounds show

poor selectivity between receptor subtypes. We reasoned

that by exalting the molecular complexity of the parent

compounds, in particular through stereochemical com-

plication in the proximity of the critical cationic head of

the molecule, the chance of ﬁnding agonists able to dis-

criminate among cholinergic receptors subtypes would

increase. Therefore, we planned the synthesis of the

series of compounds with three stereogenic centres

shown in Chart 1, where the structure of nicotine is

hybridised with that of 1,3-dioxolane 1 and 1,3-oxa-

thiolane 2. The choice of the pyrrolidine ring for mole-

cular complication was due to the intent of increasing

the nicotinic activity of the 1,3-dioxolanes and 1,3-oxa-

thiolanes, while maintaining their high muscarinic

activity. Moreover, we expected that the introduction of

the pyrrolidine ring would induce activity also in the

tertiary bases, as it happens for nicotine. As a matter of

fact, the tertiary bases corresponding to 1,3-dioxolane 1

and 1,3-oxathiolane 2, are much less potent than the

iodomethylates which, in turn, are unsuitable as centrally

acting drugs. In the present communication, we report the

synthesis and the preliminary cholinergic binding proﬁle

of the four series of compounds shown in Chart 1.

1,3-Dioxolanes

Starting from the (2S)-(+)-prolinol enantiomer [(2S)-

(+)-pyrrolidinemethanol, Scheme 1], the pyrrolidine

nitrogen was ﬁrst protected as N-benzyloxycarbonyl

(CBZ) derivative, using dibenzyldicarbonate¹⁴or (with

better yields) benzylchloroformate.¹⁵On the protected

derivative (2S)-(À)-3, reactions were then performed

that allowed the building of the 1,3-dioxolane and the

1,3-oxathiolane rings, with retention of the starting

prolinol conﬁguration, as was veriﬁed by comparing the

rotatory optical activity of our intermediates with the

values already reported. In fact, compounds (2S)-(À)-

3,¹⁶(2R)-(+)-3,¹⁷(2S)-(À)-4,^18,19(2R)-(+)-4¹⁷and

(2S)-(À)-5,^20,21were known (see also the Experimental),

even if not fully characterised or synthesised in a diﬀer-

ent way; in any case comparison with the reported

rotatory optical activity conﬁrmed the retention of con-

ﬁguration on the stereocentre. (2S)-(À)-3 was therefore

oxidized to aldehyde (2S)-(À)-4 according to Parikh and

Doering,²²with low but acceptable yields, and without

racemisation. Wittig reaction on this intermediate gave

the corresponding alkene (2S)-(À)-5, that was oxidized,

in the presence of TBHP (t-butyl hydroperoxide) and of

a catalytic amount of OsO₄,²³to diol (2S)-6, as mixture

of two diastereoisomers. It is to note that one of the

isomers present in our mixture was already described.¹⁷

Subsequent cyclisation with acetaldehyde dimethylace-

tal²⁴aﬀorded the protected 1,3-dioxolane derivative

(2S)-7 as a mixture of diastereoisomers. The N-methyl

derivatives (2S)-8 were directly obtained from the pro-

tected compounds through reduction of the CBZ group

with LiAlH₄.²⁵The diastereomeric mixture (2S)-8 was

separated on an Al₂O₃chromatographic column, in

order to avoid the opening of the acid-sensitive

1,3-dioxolane ring, yielding two diastereomeric tertiary

amines [(2S, 4⁰S, 2⁰R)-(À)-8a and (2S, 4⁰R, 2⁰S)-(À)-8c]

plus traces of the other diastereoisomers (fraction b, see

the Experimental). The isomers were also transformed

into the corresponding methiodides 9.

Chemistry

Compounds 8 and 14, and their corresponding methio-

dide derivatives 9 and 15 (Chart 1), possess three stereo-

genic centres and can exist as eight diﬀerent isomers. For

their synthesis we started from two chiral precursors,

S- and R-prolinol, respectively. In both cases, only two

The same reaction sequence, performed on the (2R)-

(À)-prolinol enantiomer [(2R)-(À)-pyrrolidinemethanol,

not shown], aﬀorded the enantiomers (2R, 4⁰R, 2⁰S)-

(+)-8a and (2R, 4⁰S, 2⁰R)-(+)-8c (Chart 2) and the

corresponding methiodides 9.

1,3-Oxathiolanes

In order to synthesize the 1,3-oxathiolane derivatives

(Scheme 1), starting again from the alkene derivative

Chart 1.

S. Dei et al. / Bioorg. Med. Chem. 11 (2003) 3153–3164

3155

Scheme 1. (a) The same reactions were performed also on the (2R)-(À)-prolinol (not shown).

Stereochemistry and Conﬁgurational Analysis

(2S)-(À)-5, the key intermediate (2S)-12 was obtained

by three-step procedure. By epoxidation with

a

m-CPBA (m-chloroperbenzoic acid)²⁶derivative (2S)-10

was synthesised, which was then treated with thioacetic

acid yielding intermediate (2S)-11, and hydrolysed in

acidic conditions to the desired thiol-alcohol derivative

(2S)-12. Cyclization aﬀorded the diastereomeric mixture

(2S)-13, which was treated with LiAlH₄, as described

before for the 1,3-dioxolane compounds, yielding also in

this case a mixture of the ﬁnal compounds [(2S)-14]

which were separated on Al₂O₃chromatographic col-

umn. Two diastereomeric tertiary amines (2S, 5⁰S, 2⁰S)-

(À)-14a and (2S, 5⁰R, 2⁰R)-(À)-14c were obtained, which

were then transformed into the corresponding meth-

iodides 15.

The structure and the absolute conﬁguration of the

1

obtained compounds was assessed by 1D and 2D H

NMR (see Table 1 and the experimental part) and by

X-ray crystallography (Fig. 1). Keeping in mind that, on

the basis of Cahn, Ingold and Prelog rules, the priority

on 1,3-oxathiolane and 1,3-dioxolane rings are diﬀerent,

the absolute stereochemistry of our derivatives is that

reported in Chart 2. NMR experiments were performed

on the tertiary amines, but their results can obviously be

extended to the corresponding methiodides. The corres-

ponding members of both series show fairly similar

NMR spectra.

First of all, we identiﬁed and characterised the ¹H NMR

signals of each proton. Toward this end, in addition to

Also, in this case, the same reactions were then per-

formed also on the (2R)-(À)-prolinol enantiomer, yield-

ing the two enantiomeric (2R)-1,3-oxathiolane amines

(2R, 5⁰R, 2⁰R)-(+)-14a and (2R, 5⁰S, 2⁰S)-(+)-14c

(Chart 2) and the corresponding methiodides 15.

1

200 MHz H NMR spectra (see Experimental), 1D and

COSY experiments were performed with a 600 MHz

instrument on the two isomers of 1,3-dioxolane (+)-8a,

c and on the corresponding 1,3-oxathiolanes (+)-14a, c,

3156

S. Dei et al. / Bioorg. Med. Chem. 11 (2003) 3153–3164

which were obtained starting from R-prolinol and pos-

sess stereochemistry R on the C-2 of the pyrrolidine

ring. Of course, conclusions reached can be extended to

products (À)-8 and (À)-14, derived from S-prolinol,

since all the data indicate that they are their enantio-

Figure 1. ORTEP drawing of compound (+)-15a showing one of the

four independent molecules in the asymmetric unit.

Chart 2. Absolute conﬁguration of the obtained stereoisomers of 8

and 14.

Table 1. ¹H NMR (CDCl₃) signals of the (+)-8 and (+)-14 isomers at 600 MHz: chemical shift (d) and coupling constants (J)

(+)-8 a

(+)-14a

(+)-8 c

(+)-14c

H_A

H_B

d=5.04 ppm

J_A-Me=5.0 Hz

d=5.22 ppm

J_A-Me=5.5 Hz

d=5.03ppm

J_A-Me=4.8 Hz

d=5.24 ppm

J_A-Me=5.7 Hz

d=4.16 ppm

J_BÀD=7.4 Hz

J_BÀC=6.5 Hz

J_BÀE=3.9 Hz

d=3.99 ppm

J_BÀD=9.4 Hz

J_B-C=5.5 Hz

J_BÀE=3.2 Hz

d=4.06 ppm

J_BÀD=7.1 Hz

J_BÀC=6.7 Hz

J_BÀE=6.8 Hz

d=3.85 ppm

J_BÀD=9.4 Hz

J_BÀC=5.4 Hz

J_BÀE=7.4 Hz

H_C

H_D

H_E

d=3.94 ppm

J_{ge CÀD}=7.5 Hz

J_BÀC=6.5 Hz

d=3.03 ppm

J_{ge CÀD}=10.0 Hz

J_BÀC=5.5 Hz

d=3.87 ppm

J_{ge CÀD}=7.8 Hz

J_BÀC=6.7 Hz

d=3.05 ppm

J_{ge CÀD}=10.1 Hz

J_BÀC=5.4 Hz

d=3.71 ppm

J_{ge CÀD}=7.5 Hz

J_BÀD=7.4 Hz

d=2.87 ppm

J_{ge CÀD}=10.0 Hz

J_BÀD=9.4 Hz

d=3.67 ppm

J_{ge CÀD}=7.8 Hz

J_BÀD=7.1 Hz

d=2.80 ppm

J_{ge CÀD}=10.1 Hz

J_BÀD=9.4 Hz

d=2.37 ppm

J_BÀE=3.9 Hz

J_HÀE=8.4 Hz

J_IÀE=6.6 Hz

d=2.47 ppm

J_BÀE=3.2 Hz

J_HÀE=9.3Hz

J_IÀE=6.6 Hz

d=2.45 ppm

J_BÀE=6.8 Hz

d=2.53ppm

J_BÀE=7.4 Hz

H_F

H_G

d=3.12 ppm

J_{ge FÀG}=9.3Hz

d=3.10 ppm

J_{ge FÀG}=9.6 Hz

d=3.07 ppm

J_{ge FÀG}=9.0 Hz

d=3.09 ppm

J_{ge FÀG}=9.3Hz

d=2.25 ppm

d=2.24 ppm

d=2.25 ppm

d=2.28 ppm

J_{ge FÀG}=9.3Hz

J_{ge FÀG}=9.6 Hz

J_{ge FÀG}=9.0 Hz

J_{ge FÀG}=9.3Hz

CH₂CH_ICH_H

H_I

H_H

d=1.71–1.76 ppm

d=1.76–1.83ppm

d=1.49–1.55 ppm

d=1.65–2.00 ppm

d=1.85–1.95 ppm

d=1.55–1.65 ppm

d=1.69–1.89 ppm

d=1.68–1.92 ppm

CH₃

d=1.41 ppm

J_A-Me=5.0 Hz

d=1.57 ppm

J_A-Me=5.5 Hz

d=1.39 ppm

J_A-Me=4.8 Hz

d=1.59 ppm

J_A-Me=5.7 Hz

N-CH₃

d=2.41 ppm

d=2.42 ppm

d=2.48 ppm

d=2.52 ppm

S. Dei et al. / Bioorg. Med. Chem. 11 (2003) 3153–3164

3157

mers. The chemical shifts and the coupling constants of

the protons of isomers (+)-8a, c and (+)-14a, c are

reported in Table 1.

Results and Discussion

The binding aﬃnity of the compounds synthesised on

rat brain nicotinic and muscarinic receptors has been

evaluated. The compounds did not show any appreci-

able aﬃnity for nicotinic receptors labelled by [³H] cyti-

sine up to the dose of 10 mM. On the contrary, most of

them showed aﬃnity in the same range of carbachol for

the muscarinic receptors labeled by [³H] N-methyl sco-

polamine ([³H] NMS). Among tertiary bases only (+)-

14c, belonging to the 1,3-oxathiolane series, shows aﬃ-

nity for muscarinic receptors (K_i=21.7Æ2.6 mM,

pK_i=4.66) comparable to that of carbachol. All other

tertiary bases, did not show aﬃnity up to the dose of

100 mM. As expected, methiodides were much more

aﬃnitive for muscarinic receptors, and their data are

reported in Table 2.

1,3-Dioxolanes

With regard to the 1,3-dioxolane derivatives (+)-8a, c,

1

the H NMR spectra of the two isomers show clear-cut

diﬀerences in the chemical shift of some protons (Table

1). Among these, the most evident regards the H_Hpro-

ton (trans with respect to H_E), that is remarkably shiel-

ded in (+)-8c with respect to the corresponding protons

of isomer (+)-8a. 2D 600 MHz NOESY experiments

were performed on the same substances, in order to

obtain information on the spatial arrangement of the

groups. The NOESY spectra indicate a clear interaction

between H_Aand H_Bfor the compounds (+)-8a and

(+)-8c, whereas there is no interaction between H_Band

the CH₃group. These ﬁndings clearly indicate that, with

respect to the 1,3-dioxolane ring, the substituents are in

a cis geometry in compounds (+)-8a and (+)-8c. We

also identiﬁed all other protons (Table 1).

The ﬁrst result to mention is the complete lack of aﬃn-

ity for the brain nicotinic receptors. From this point of

view, our eﬀort to design compounds endowed, at the

same time, with nicotinic and muscarinic aﬃnity has

unexpectedly failed. Even if the comparison of the

results is diﬃcult, since the nicotinic activity of 1⁹and

1,3-Oxathiolanes

2

¹²was determined by functional assays on a peripheral

The 1D and 2D spectra of the 1,3-oxathiolane deriva-

tives (+)-14 give information that strictly parallels

that of the corresponding 1,3-dioxolanes (Chart 2,

Table 1). Thus, the evaluation of the COSY spectrum

shows a shielding eﬀect of about 0.3ppm, with respect

to the other isomer, on the H_Hsignal of the com-

pound (+)-14c, as already shown by the correspond-

ing 1,3-dioxolane.

nicotinic receptors model such as the frog rectus abdo-

minis, stereochemical complication seems to have

destroyed the nicotinic activity present in the parent

compounds.

However, as far as muscarinic aﬃnity is concerned the

results were much more interesting. One tertiary base

[(+)-14c] belonging to the 1,3-oxathiolane series showed

a good aﬃnity for the central muscarinic receptors which

makes it promising as potential central acting drug. As

The NOESY spectra also show in this case that sub-

stituents of compounds (+)-14a and (+)-14c present a

cis geometry in the 1,3-oxathiolane ring; even if in the

1,3-oxathiolane isomers, unlike in the corresponding cis

1,3-dioxolane derivatives (+)-8a and (+)-8c, it was not

possible to directly evaluate the interaction between H_A

and H_C. This fact could be related to the greater

dimensions of the sulphur with respect to the oxygen,

that modify the structure of the pentatomic ring and

send away H_Afrom H_C. The data of all other protons

are reported in Table 1.

Table 2. Binding aﬃnity of methyl iodide derivatives 9 and 15 on the

rat brain muscarinic receptors

Drug

Stereochemistry

binding^a

K_i(mM)

(ÆSEM)

ER^b

pK_i

An attempt was made to establish the absolute stereo-

chemistry of both 1,3-dioxolanes and 1,3-oxathiolanes

on the basis of NOESY spectra, but the data did not

allow any sound attribution. The absolute conﬁguration

of 1,3-oxathiolane compounds could be established by

X-ray crystallography of methiodide (+)-15a, whose

crystallographic structure is shown in Figure 1.

(À)-9a

2S, 4⁰S, 2⁰R

>100

—

>7.94

>5.21

4.58

(+)-9a

(À)-9c

2R, 4⁰R, 2⁰S

2S, 4⁰R, 2⁰S

12.6Æ3.7

19.2Æ2.8

4.90

4.72

(+)-9c

(À)-15a

2R, 4⁰S, 2⁰R

2S, 5⁰S, 2⁰S

>100

27.0Æ3.8

—

4.56

The crystal structure conﬁrmed that the 2⁰and 5⁰side

chains are in a cis geometry and shows that its absolute

conﬁguration is 2R, 5⁰R, 2⁰R. The structure of the other

1,3-oxathiolane methiodides and of the corresponding

tertiary bases is straightforward. The absolute conﬁgur-

ation of the 1,3-dioxolane compounds was attributed on

(+)-15a

(À)-15c

2R, 5⁰R, 2⁰R

2S, 5⁰R, 2⁰R

5.9Æ0.6

7.3Æ0.8

5.23

5.14

1.25

(+)-15c

Carbachol

2R, 5⁰S, 2⁰S

9.1Æ1.1

5.04

4.38

41.3Æ7.0

^aOn rat brain homogenates. The muscarinic receptors were labelled by

[³H] N-methyl scopolamine ([³H] NMS). See the pharmacological

experimental part for details (n=3experiments).

^bEudismic ratio. The eudismic ratio is the ratio: (aﬃnity of the dis-

tomer)/(aﬃnity of the eutomer).

1

the basis of the strict similarity of their H NMR and

¹³C NMR spectra with those of the corresponding

1,3-oxathiolanes.

3158

S. Dei et al. / Bioorg. Med. Chem. 11 (2003) 3153–3164

expected, iodomethylates were much more aﬃnitive for

brain muscarinic receptors (Table 2). All 1,3-oxathio-

lane derivatives 15 showed aﬃnity larger than that of

carbachol, some of them being almost an order of

magnitude more aﬃnitive. At the contrary, only (+)-9a

and (À)-9c among the 1,3-dioxolane derivatives showed

aﬃnity of the same order of magnitude of carbachol.

probably due to the molecular complication introduced

which might induce slight changes in the mode of

binding of the ligands to the receptor recognition site.

Of course, the results presented have to be considered

preliminary. A screening on the ﬁve cloned human

muscarinic subtypes (m_1À5) and the evaluation of the

agonistic activity on available functional tests for mus-

carinic receptors (M_1À4), which are already under way,

will be necessary to fully evaluate the pharmacological

proﬁle of this new set of compounds and to appreciate

their usefulness for receptor characterisation and for

drug development. Considering the large conservation

in the structure of the recognising sites of the ﬁve known

muscarinic receptors,^27,28it is hoped that these stereo-

chemically complex agonists, which are in principle able

to detect subtle structural diﬀerences, will help to over-

come the diﬃculties in designing subtype selective mus-

carinic agonists.

In principle, the molecular complication introduced into

the structure of parent compounds could alter their

pharmacological properties changing agonism into

antagonism. This does not seem to be the case since, as

shown by the dose–response curve reported in Figure 2,

compound (+)-9a behaves as a full agonist on guinea

pig ileum (M₃), showing an intrinsic activity of a=0.95

and a Àlog ED₅₀=6.65. Therefore, the changes intro-

duced into the molecule seem to leave the intrinsic

activity on muscarinic receptor unchanged. Of course,

the functional pharmacological proﬁle of the other

members of the series need to be individually measured

and this study will be reported in due time.

Experimental

Chemistry

It is interesting to compare the absolute conﬁguration of

the most aﬃnitive compounds with that of the parent

compounds. The compounds of the 1,3-dioxolane series

that show muscarinic aﬃnity comparable to that of

carbachol [(+)-9a and (À)-9c] have the 2⁰S, 4⁰R con-

ﬁguration, which is precisely that of the most potent

enantiomer of 1 (2S,4R).^11,13In the 1,3-oxathiolane

series, the most aﬃnitive compound (+)-15a has the

2⁰R,5⁰R absolute conﬁguration, which is identical to that

of the most active enantiomer of 2 (2R,5R), and the

same happens for (À)-15c (2⁰R,5⁰R), which is only

slightly less aﬃnitive. However, its enantiomer (+)-15c

(2⁰S, 5⁰S) shows almost the same aﬃnity. In general,

there is a fairly good correspondence between the abso-

lute conﬁguration of the most active enantiomers of the

parent compounds and the aﬃnity of the most aﬃnitive

representative of the new series. Minor discrepancies are

All melting points were taken on a Buchi apparatus and

are uncorrected. Infrared spectra were recorded with a

Perkin-Elmer 681 spectrophotometer in Nujol mull for

solids and neat for liquids. Unless otherwise stated,

NMR spectra were recorded on a Gemini 200 spectro-

1

meter (200 MHz for H NMR, 50.3MHz for ¹³C), and

chromatographic separations were performed on a silica

gel column by gravity chromatography (Kieselgel 40,

0.063–0.200 mm; Merck) or ﬂash chromatography

(Kieselgel 40, 0.040–0.063mm; Merck). When neces-

sary, chromatographic separation were performed on an

Al₂O₃column by gravity chromatography (Aluminium

oxide 90 standardized, Merck). Yields are given after

puriﬁcation, unless otherwise stated. Where analyses are

indicated by symbols, the analytical results are within

Æ0.4% of the theoretical values. Optical rotation was

measured at a concentration of 1 g/100 mL (c=1),

unless otherwise stated, with a Perkin-Elmer polari-

meter (accuracyÆ0.002^ꢀ).

(2S)-(À)-Phenylmethyl 2-(hydroxymethyl)pyrrolidine-1-

carboxylate [S-(À)-3].¹⁶Method A. To a solution of

2.5 g (24.7 mmol) of l-prolinol [(2S)-(+)-pyrrolidine-

methanol] in NaOH 1 N (25 mL) and dioxane (25 mL),

dibenzyl dicarbonate (7.1 g, 24.8 mmol) in dioxane

(25 mL) was added. After 5 h at room temperature, the

bulk of dioxane was evaporated and the resulting aqu-

eous solution acidiﬁed with H₂SO₄1 N to pH 2 and

extracted three times with ethyl acetate. The organic layer

were dried over Na₂SO₄and evaporated. The residue was

puriﬁed by ﬂash chromatography (eluent CHCl₃100).

3.1 g (13.2 mmol, 53% yield) of S-(À)-3 were obtained.

Method B. An ice-cold solution of l-prolinol (2.5 g,

24.7 mmol) in a mixture of 2 M Na₂CO₃aqueous solu-

tion/dioxane (4:1, 125 mL) was treated dropwise with vig-

orous stirring with benzyl chloroformate (8.6 mL,

60.24 mmol) dissolved in 50mL dioxane. Simultaneously,

Figure 2. & Dose–response curve of reference agonist arecaidine pro-

pargyl ester (APE); ^ dose–response curve of agonist (+)-9a on gui-

nea pig ileum (M₃). Each point is the mean of at least six independent

observations. The SEMs are less than 10% and are not shown.

S. Dei et al. / Bioorg. Med. Chem. 11 (2003) 3153–3164

3159

1

aqueous 2 M NaOH (31 mL) was added. After 3 h, most

of the dioxane was evaporated, and the remaining sus-

pension was extracted three times with diethyl ether.

The combined extracts were dried over Na₂SO₄and

evaporated to aﬀord a residue that was puriﬁed by ﬂash

chromatography (eluent CHCl₃100). 4.8 g (20.4 mmol,

85% yield) of title compound were obtained.

bamate). H NMR (CDCl₃) d (ppm): 1.70–2.30 (m, 4H,

CH₂CH₂); 3.40–3.60 (m, 2H, CH₂N); 4.07–4.18 (m, 1H,

CHN); 5.14 (s, 0.5+0.5H) and 5.17 (s, 0.5+0.5H)

(CH₂Ph); 7.20–7.40 (m, 5H, aromatics); 9.54 (d,

J=20.6 Hz, 0.5H) and 9.55 (d, J=20.6 Hz, 0.5H)

(CHO). Anal. (C₁₃H₁₅NO₃): C, H, N.

(2S)-(À)-Phenylmethyl 2-vinylpyrrolidine-1-carboxylate

[S-(À)-5].^20,21To a suspension of 8.1 g (22.7 mmol) of

methyl triphenylphosphonium bromide in anhyd THF

in ice-bath under nitrogen, a solution of 17.5 mL of

n-BuLi 1.6 M in hexane was added. The resulting solu-

tion was maintained 20 min at 0 ^ꢀC and 15 min at rt, and

treated with 5.3g (22.7 mmol) of S-(À)-4 dissolved in

anhyd THF. The mixture was stirred 2 h at rt, reﬂuxed

for 2 h, poured on ice and extracted with diethyl ether.

The organic layer was washed twice with a saturated

solution of NH₄Cl, dried over Na₂SO₄and concentrated

in vacuo to give a residue that was puriﬁed by ﬂash chro-

matography on silica gel (eluent CH₂Cl₂/MeOH 98:2)

yielding 2.5 g (10.8 mmol, 47% yield) of S-(À)-5.

½a^D₂₀=À16.1^ꢀ(CHCl₃) (½a₂^D₀=À9^ꢀ(CH₂Cl₂)²¹) IR

(neat) n (cm^À1): 1705 (C¼O), ¹H NMR (CDCl₃) d

(ppm): 1.70–2.10 (m, 4H, CH₂CH₂); 3.40–3.57 (m, 2H,

CH₂N); 4.31–4.50 (m, 1H, CHN); 4.95–5.15 (m, 4H,

CH₂Ph+CH₂¼); 5.65–5.90 (m, 1H, CH¼); 7.25–7.40

(m, 5H, aromatics). Anal. (C₁₄H₁₇NO₂): C, H, N.

½a^D₂₀=À40.2^ꢀ(CHCl₃) (½a₂^D₀=À42.4^ꢀ(CHCl₃)¹⁶), IR

(neat) n (cm^À1): 3700–3200 (OH); 1690 (C¼O), ¹H

NMR (CDCl₃) d (ppm): 1.30–2.10 (m, 4H, CH₂CH₂);

3.30–3.70 (m, 5H, CH₂N+CH₂O+OH); 3.90–4.06 (m,

1H, CHN); 5.18 (s, 2H, CH₂Ph); 7.39 (s, 5H, aro-

matics). Anal. (C₁₃H₁₇NO₃): C, H, N.

(2R)-(+)-Phenylmethyl 2-(hydroxymethyl)pyrrolidine-1-

carboxylate [R-(+)-3].¹⁷Using procedure B described

for S-(À)-3, and starting from 5 g (49.4 mmol) of d-

prolinol [(2R)-(À)-pyrrolidinemethanol] and 17.2 mL

(120.5 mmol) of benzyl chloroformate, crude R-(+)-3

was obtained. The residue was puriﬁed by ﬂash chro-

matography

(43.4 mmol, 88% yield) of title compound.

(eluent

CHCl₃)

aﬀording

10.2 g

½a^D₂₀=+41.2^ꢀ(CHCl₃) (½a₂^D₀=+40^ꢀ(CHCl₃)¹⁷), IR

(neat) n (cm^À1): 3650–3200 (OH); 1685 (C¼O), ¹H

NMR (CDCl₃) d (ppm): 1.55–2.05 (m, 4H, CH₂CH₂);

3.30–3.70 (m, 5H, CH₂N+CH₂O+OH); 3.90–4.10 (m,

1H, CHN); 5.08 (s, 2H, CH₂Ph); 7.40 (s, 5H, aro-

matics). Anal. (C₁₃H₁₇NO₃): C, H, N.

(2R)-(+)-Phenylmethyl 2-vinylpyrrolidine-1-carboxylate

[R-(+)-5]. Using the same procedure described for

S-(À)-5, and starting from 6.5 g (27.9 mmol) of R-(+)-4,

10.0 g (27.9 mmol) of methyl triphenylphosphonium

bromide and 21.66 mL of n-BuLi 1.6 M in hexane,

R-(+)-5 crude was obtained, that was puriﬁed by ﬂash

chromatography (eluent CH₂Cl₂/MeOH 98:2). Yield

2.9 g (12.5 mmol, 45%). ½a^D₂₀=+17.3^ꢀ(CHCl₃), IR

(neat) n (cm^À1): 1700 (C¼O), ¹H NMR (CDCl₃) d

(ppm): 1.63–2.15 (m, 4H, CH₂CH₂); 3.40–3.59 (m, 2H,

CH₂N); 4.35–4.45 (m, 1H, CHN); 4.97–5.21 (m, 4H,

CH₂Ph+CH₂¼); 5.68–5.90 (m, 1H, CH¼); 7.30–7.45

(m, 5H, aromatics). Anal. (C₁₄H₁₇NO₂): C, H, N.

(2S)-(À)-Phenylmethyl 2-formylpyrrolidine-1-carboxy-

late [S-(À)-4].^18,19To 7.9 g (33.6 mmol) of S-(À)-3, a

solution of 14.1 mL of an. triethylamine in 100 mL of

anhyd dimethyl sulfoxide and a solution of 16.0 g

(100.8 mmol) of sulfur trioxide–pyridine complex dis-

solved in 100 mL of anhyd dimethyl sulfoxide were

added at rt. The reaction mixture was stirred for 2 h and

poured into ice-water. The mixture was extracted twice

with diethyl ether, and the combined organic layers

were successively washed twice with 10% aqueous citric

acid, water and saturated aqueous NaHCO₃, and dried

over Na₂SO₄. The solvent was concentrated in vacuo to

give 5.3g (22.7 mmol) of S-(À)-4. Yield 67%.

½a^D₂₀=À83.1^ꢀ(CHCl₃) (½a^D₂₀=À78.1^ꢀ(CH₂Cl₂),¹⁹½a₂^D₀=

À40.8^ꢀ(MeOH)¹⁸), IR (neat) n (cm^À1): 1730 (C¼O alde-

hyde); 1700 (C¼O carbamate), ¹H NMR (CDCl₃) d

(ppm): 1.70–2.30 (m, 4H, CH₂CH₂); 3.40–3.65 (m, 2H,

CH₂N); 4.20–4.40 (m, 1H, CHN); 5.14 (s, 0.5+0.5H)

and 5.18 (s, 0.5+0.5H) (CH₂Ph); 7.20–7.40 (m, 5H,

aromatics); 9.55 (d, J=21.0 Hz, 0.5H) and 9.56 (d,

J=21.0 Hz, 0.5H) (CHO). Anal. (C₁₃H₁₅NO₃): C, H, N.

(2S)-(À)-Phenylmethyl

2-(1,2-dihydroxyethyl)pyrroli-

dine-1-carboxylate [(2S)-6].¹⁷1.5 g (6.5 mmol) of S-(À)-

5, 1.59 mL (16.5 mmol) of t-butyl hydroperoxide

(TBHP) 70% and 480 mg (1.8 mmol) of tetra-

.

ethylammonium acetate tetrahydrate (Et₄NOAc 4H₂O)

were combined in 19 mL of acetone. The solution was

cooled at 0 ^ꢀC and 6.4 mL of the OsO₄solution (250 mg

of OsO₄in 50 mL of t-butyl alcohol) were added in one

portion. After 1 h, the ice bath was removed and the

mixture was left for 10 h at rt. Then, 38.1 mL of diethyl

ether were added to the solution, and the mixture was

cooled by stirring in an ice-bath; 12.7 mL of 10%

NaHSO₃were added. The ice bath was then removed

and stirring continued for 1 h. NaCl was added to satu-

rate the aqueous layer and stirring was continued for

15 min. The phases were partitioned in a separatory fun-

nel, the organic phase was washed with brine, and the

aqueous layer re-extracted with ether. The combined

organic layers were dried over Na₂SO₄and concentrated

in vacuo to aﬀord a residue which, after ﬂash chroma-

(2R)-(+)-Phenylmethyl 2-formylpyrrolidine-1-carboxyl-

ate [R-(+)-4].¹⁷Using the same procedure described

for S-(À)-4 and starting from 10.2 g (43.4 mmol) of

R-(+)-3, 18 mL of anhyd triethylamine and 20.7 g

(130.2 mmol) of sulfur trioxide–pyridine complex, 6.5 g

(27.9 mmol) of R-(+)-4 were obtained (yield 64%).

½a^D₂₀=+82.1^ꢀ(CHCl₃) (½a₂^D₀=+83^ꢀ(CHCl₃)¹⁷) IR

(neat) n (cm^À1): 1730 (C¼O aldehyde); 1700 (C¼O car-

3160

S. Dei et al. / Bioorg. Med. Chem. 11 (2003) 3153–3164

tography (eluent CH₂Cl₂/MeOH 98:2) gave 1.24 g

(4.7 mmol, 72% yield) of (2S)-6 as a mixture of two

diastereoisomers.

CH₃CH); 1.70–2.06 (m, 4H, CH₂CH₂); 3.15–4.52 (m,

6H, CH₂O+CH₂N+CHO+CHN); 4.92–5.20 (m, 3H,

CH₂Ph+CHCH₃); 7.30–7.45 (m, 5H, aromatics). Anal.

(C₁₆H₂₁NO₄): C, H, N.

½a^D₂₀=À42.8^ꢀ(CHCl₃) (½a₂^D₀=À20^ꢀ(CHCl₃) reported

by Mazzini¹⁷for one of the two diastereoisomers), IR

(neat) n (cm^À1): 3700–3100 (OH); 1680 (C¼O), ¹H

NMR (CDCl₃) d (ppm): 1.68–2.17 (m, 4H, CH₂CH₂);

2.60–2.98 (bs, 2H, OH+OH); 3.30–3.46 (m, 2H,

CH₂N); 3.50–3.70 (m, 3H, CH₂O+CHN); 3.88–4.00

(m, 0.5H) and 4.00–4.15 (m, 0.5H) (CHO); 5.12 (s, 2H,

CH₂Ph); 7.30–7.45 (m, 5H, aromatics). Anal.

(C₁₄H₁₉NO₄): C, H, N.

(2S, 4⁰S, 2⁰R)-1-Methyl-2-(2-methyl-1,3-dioxolan-4-yl)

pyrrolidine [(À)-8a] and (2S, 4⁰R, 2⁰S)-1-methyl-2-(2-

methyl-1,3-dioxolan-4-yl)pyrrolidine [(À)-8c]. A solution

of 1.13g (3.9 mmol) of (2S)-7 dissolved in the minimum

amount of anhyd THF was added dropwise to a sus-

pension of 0.97 g (25.5 mmol) of LiAlH₄in anhyd THF

at À18 ^ꢀC under nitrogen. The mixture was allowed to

reach room temperature, and after 4 h was treated with

brine and extracted with ethyl acetate. The organic layer

was dried over Na₂SO₄and concentrated in vacuo to

aﬀord an oil, (2S)-8 as a mixture of three isomers, that

was puriﬁed by column chromatography on Al₂O₃

(eluent CH₂Cl₂/MeOH 99:1). The chromatographic

separation yielded 160 mg of isomer a, 120 mg of the

isomer c and another fraction of unidentiﬁed isomers

(2R)-Phenylmethyl 2-(1,2-dihydroxyethyl)pyrrolidine-1-

carboxylate [(2R)-6].¹⁷Using the same procedure

described for (2S)-6, and using 2.0 g (8.6 mmol) of

R-(+)-5, 2.12 mL (22.0 mmol) of TBHP 70%, 640 mg

.

(2.4 mmol) of Et₄NOAc 4H₂O and 8.5 mL of the OsO₄

solution in t-butyl alcohol, (2R)-6 was obtained and

puriﬁed by ﬂash chromatography (eluent CH₂Cl₂),

aﬀording 1.66 g (6.3mmol, 72% yield) of product as a

mixture of two diastereoisomers.

(fraction b), with a total yield of 320 mg (1.9 mmol,

D

48%). Elemental analysis and ½a of each isomer are

20

reported in Table 3. Hydrogens are deﬁned in Table 1.

½a^D₂₀=+41.8^ꢀ(CHCl₃) (½a₂^D₀=+66^ꢀ(CHCl₃) reported

by Mazzini¹⁷for one of the two diastereoisomers), IR

(neat) n (cm^À1): 3700–3100 (OH); 1685 (C¼O), ¹H

NMR (CDCl₃) d (ppm): 1.70–2.20 (m, 4H, CH₂CH₂);

2.95–3.20 (bs, 2H, OH+OH), 3.25–3.74 (m, 5H,

CH₂N+CH₂O+CHN); 3.85–4.00 (m, 0.5H) and 4.00–

4.07 (m, 0.5H) (CHO); 5.08 (s, 2H, CH₂Ph); 7.30–7.45

(m, 5H, aromatics). Anal. (C₁₄H₁₉NO₄): C, H, N.

(À)-8a. ¹H NMR (CDCl₃)

d (ppm): 1.41 (d,

J=5.0 Hz, 3H, CH₃CH); 1.65–1.90 (m, 4H, CH₂CH₂);

2.15–2.40 (m, 2H, CHH_GN and CH_EN), 2.41 (s, 3H,

CH₃N), 3.08–3.16 (m, 1H, CH_FHN), 3.67–3.75 (m, 1H,

CH_DHO), 3.90–3.97 (m, 1H, CHH_CO), 4.12–4.20 (m,

OCH_B), 5.04 (q, J=5.0 Hz, CHCH₃).

(2S)-Phenylmethyl 2-(2-methyl-1,3-dioxolan-4-yl)pyrroli-

dine-1-carboxylate [(2S)-7]. To a solution of 1.24 g

(4.7 mmol) of (2S)-6 in 26 mL of 2-propanol, 120 mg

(0.6 mmol) of p-toluensulfonic acid monohydrate were

added. To this solution, 3.6 mL (33.9 mmol) of acetal-

dehyde dimethyl acetal were added, and the mixture was

kept to reﬂux for 2 h and concentrated in vacuo. The

residue was dissolved in 60 mL of diethyl ether, and the

organic layer was washed with 40 mL of water and dried

over Na₂SO₄. Evaporation of the solvent gave an oily

residue that was puriﬁed by column chromatography on

Al₂O₃as a mixture of isomers (eluent: CHCl₃/MeOH

99:1). Yield 1.13g (3.9 mmol, 83%) of (2S)-7.

(À)-8c. ¹H NMR (CDCl₃)

d (ppm): 1.39 (d,

J=5.0 Hz, 3H, CH₃CH); 1.45–1.85 (m, 4H, CH₂CH₂);

2.16–2.48 (m, 2H, CHH_GN and CH_EN), 2.48 (s, 3H,

CH₃N), 3.00–3.14 (m, 1H, CH_EHN), 3.67–3.75 (m, 1H,

CH_DHO), 3.89–3.99 (m, 1H, CHH_CO), 3.98–4.08 (m,

OCH_B), 5.00 (q, J=5.0 Hz, CHCH₃).

Isomeric amines were transformed in the corresponding

oxalate by treatment with one equivalent of oxalic acid

in ethyl acetate (Table 3).

(2R, 4⁰R, 2⁰S)-1-Methyl-2-(2-methyl-1,3-dioxolan-4-yl)

pyrrolidine [(+)-8a] and (2R, 4⁰S, 2⁰R)-1-methyl-2-(2-

methyl-1,3-dioxolan-4-yl)pyrrolidine [(+)-8c]. With the

same procedure described for (2S)-8 and using 1.5 g

½a^D₂₀=À60.5^ꢀ(CHCl₃), IR (neat) n (cm^À1): 1710 (C¼O),

¹H NMR (CDCl₃) d (ppm): 1.18–1.42 (m, 3H, CH₃CH);

1.70–2.08 (m, 4H, CH₂CH₂); 3.27–4.50 (m, 6H,

CH₂O+CH₂N+ CHO+CHN); 4.92–5.23(m, H3,

CH₂Ph+CHCH₃); 7.30–7.45 (m, 5H, aromatics). Anal.

(C₁₆H₂₁NO₄): C, H, N.

(5.1 mmol) of (2R)-7 and 1.3g (34.2 mmol) of LiAlH ,

4

(2R)-8 was obtained as a mixture of isomers, that were

separated by column chromatography on Al₂O₃(eluent

CH₂Cl₂100). Separation aﬀorded 240 mg of isomer a,

110 mg of isomer c and another fraction of unidentiﬁed

isomers (fraction b). Total yield 390 mg (2.3 mmol,

D

(2R)-Phenylmethyl 2-(2-methyl-1,3-dioxolan-4-yl)pyrrol-

idine-1-carboxylate [(2R)-7]. With the same procedure

described for (2S)-7, using 1.66 g (6.3mmol) of (2R)-6,

4.65 mL (44.0 mmol) of acetaldehyde dimethyl acetal,

1.56 g (5.4 mmol, 85% yield) of a mixture of isomers of

(2R)-7 were obtained.

45%). Elemental analysis and ½a of each isomer are

20

reported in Table 3. Hydrogens are deﬁned in Table 1.

(+)-8a. ¹H NMR (CDCl₃)

d (ppm): 1.41 (d,

J=5.0 Hz, 3H, CH₃CH); 1.64–1.89 (m, 4H, CH₂CH₂);

2.16–2.40 (m, 2H, CHH_GN and CH_EN), 2.41 (s, 3H,

CH₃N), 3.08–3.15 (m, 1H, CH_FHN), 3.66–3.75 (m, 1H,

CH_DHO), 3.89–3.96 (m, 1H, CHH_CO), 4.12–4.20 (m,

½a₂^D₀=+62.7^ꢀ(CHCl₃), IR (neat) n (cm^À1): 1705

1

(C¼O), H NMR (CDCl₃) d (ppm): 1.22–1.40 (m, 3H,

S. Dei et al. / Bioorg. Med. Chem. 11 (2003) 3153–3164

3161

Table 3. Chemical and physical characteristics of derivatives 8 and 14

and 5.15 (s, 0.5+0.5H) (CH₂Ph); 7.30–7.45 (m, 5H,

aromatics). Anal. (C₁₄H₁₇NO₃): C, H, N.

D

20

Compd Stereochemistry Mp (oxalate)^a

(^ꢀC)

½ꢀ

Analysis

(CH₂Cl₂)

(2S)-Phenylmethyl 2-(1-hydroxy-2-mercaptoethyl)pyrro-

lidine-1-carboxylate [(2S)-12]. 900 mg (3.6 mmol) of

(2S)-10 were reacted with 270 mg (3.6 mmol) of thio-

acetic S-acid for 12 h at 60 ^ꢀC in anhyd conditions. The

excess thioacetic acid was removed under reduced pres-

sure, the residue dissolved in CHCl₃and washed twice

with a saturated solution of Na₂CO₃and twice with

water, and dried over Na₂SO₄. Evaporation of the sol-

vent gave 990 mg of (2S)-phenylmethyl 2-(2-acetyl-

sulfanyl-1-hydroxyethyl)pyrrolidine-1-carboxylate [(2S)-

11]. IR (neat) n (cm^À1): 3600–3250 (OH); 1750 (C¼O

(À)-8a

2S,4⁰S, 2⁰R

2S,4⁰R, 2⁰S

2R,4⁰R, 2⁰S

2R,4⁰S, 2⁰R

2S,5⁰S, 2⁰S

2S,5⁰R, 2⁰R

2R,5⁰R, 2⁰R

2R,5⁰S, 2⁰S

108–110

96–98

107–109

94–96

116–118

92–95

115–118

90–93+C60.3

À16.7

À44.9

+17.2

+46.7

À24.5

À62.1

+25.4

C₉H₁₇NO₂

C₉H₁₇NOS

₉H₁₇NOS

(À)-8c

(+)-8a

(+)-8c

(À)-14a

(À)-14c

(+)-14a

(+)-14c

^aFrom abs ethanol/diethyl ether.

OCH_B), 5.04 (q, J=5.0 Hz, CHCH₃); ¹³C NMR

(CDCl₃) d (ppm): 19.90 (q), 23.52 (t), 26.27 (t), 41.89

(q), 58.23(t), 67.24 (d), 67.82 (t), 77.17 (d), 102.03(d).

1

thioacetyl); 1700 (C¼O carbamate). H NMR (CDCl₃)

d (ppm): 1.80–2.05 (m, 4H, CH₂CH₂); 2.35 (s, 3H,

CH₃C¼O);

2.75–4.40

(m,

6H,

CH₂N+

CH₂S+CHN+CHO); 5.15 (s, 2H, CH₂Ph); 7.30–7.45

(m, 5H, aromatics). The TLC indicated the presence of

two isomers. The compound was used as such without

further characterization. (2S)-11 was dissolved in

5.5 mL of MeOH and 0.22 mL of concd HCl were

added. The solution was kept at 60 ^ꢀC for 6 h. Evap-

oration of the solvent yielded 910 mg of (2S)-12 as a

mixture of two diastereoisomers. Yield 90%.

(+)-8c. ¹H NMR (CDCl₃)

d (ppm): 1.39 (d,

J=4.8 Hz, 3H, CH₃CH); 1.45–1.85 (m, 4H, CH₂CH₂);

2.20–2.30 (m, 1H, CHH_GN), 2.31–2.45 (m, 1H, CH_EN),

2.48 (s, 3H, CH₃N), 3.00–3.13 (m, 1H, CH_FHN), 3.67–

3.75 (m, 1H, CH_DHO), 3.88–3.99 (m, 1H, CHH_CO),

4.08–4.20 (m, OCH_B), 5.02 (q, J=4.8 Hz, CHCH₃). ¹³C

NMR (CDCl₃) d (ppm): 20.21 (q), 23.90 (t), 27.27 (t),

42.55 (q), 58.37 (t), 67.48 (d), 67.64 (t), 80.22 (d), 102.24

(d).

1

IR (neat) n (cm^À1): 3600–3200 (OH); 1690 (C¼O), H

NMR (CDCl₃) d (ppm): 1.65–2.05 (m, 4H, CH₂CH₂);

2.45–2.80 (m, 2H, CH₂S); 3.30–3.45 (m, 2H, CH₂N);

3.50–4.17 (m, 2H, CHO+CHN); 4.22–4.50 (bs, 2H,

OH+SH); 5.15 (s, 2H, CH₂Ph); 7.30–7.45 (m, 5H, aro-

matics). Anal. (C₁₄H₁₉NO₃S): C, H, N.

Each isomeric amine was transformed in the corre-

sponding oxalate by treatment with one equivalent of

oxalic acid in ethyl acetate (Table 3).

(2S)-Phenylmethyl 2-oxiran-2-ylpyrrolidine-1-carboxy-

late [(2S)-10]. To a solution of 920 mg (4.0 mmol) of S-

(À)-5 in dry CH₂Cl₂at 0 ^ꢀC a solution of 1.38 g

(8.0 mmol) of m-chloroperbenzoic acid (mCPBA) in dry

CH₂Cl₂was added. After being stirred at rt for 4 h, the

mixture was kept at 50 ^ꢀC for 1 h. The mixture was ﬁl-

tered, and the ﬁltrate was washed successively with

saturated Na₂CO₃, saturated NaHCO₃and water, and

dried over Na₂SO₄. The organic layer was concentrated

in vacuo yielding 900 mg (3.61 mmol, 90% yield) of the

title product (2S)-10 as a mixture of two diastereo-

isomers.

(2R)-Phenylmethyl 2-(1-hydroxy-2-mercaptoethyl)pyrrol-

idine-1-carboxylate [(2R)-12]. Using the same procedure

described for (2S)-11 and starting from 1.41 g

(5.7 mmol) of (2R)-10 and 430 mg (5.7 mmol) of thioa-

cetic S-acid, 1.53g of (2R)-phenylmethyl 2-(2-acetyl-

sulfanyl-1-hydroxyethyl)pyrrolidine-1-carboxylate [(2R)-

11] were obtained. The TLC showed the presence of two

diastereoisomers. IR (neat) n (cm^À1): 3600–3250 (OH);

1750 (C¼O thioacetyl); 1695 (C¼O carbamate). ¹H

NMR (CDCl₃) d (ppm): 1.75–2.15 (m, 4H, CH₂CH₂);

2.35 (s, 3H, CH₃C¼O); 2.67–4.20 (m, 6H,

CH₂N+CH₂S+CHN+CHO); 5.12 (s, 2H, CH₂Ph);

7.30–7.45 (m, 5H, aromatics). The compound was used

as such without further characterization. (2R)-11 was

dissolved in 8.64mL of MeOH and 0.33mL of concd HCl

were added. The solution was kept at 60^ꢀC for 6 h. Eva-

poration of the solvent yielded 1.38g (4.9 mmol) of (2R)-

12 as a mixture of two diastereoisomers in 86% yield.

½a^D₂₀=À15.6^ꢀ(benzene), ¹H NMR (CDCl₃) d (ppm):

1.80–2.10 (m, 4H, CH₂CH₂); 2.45–3.10 (m, 3H, CHCH₂

epoxide); 3.30–3.55 (m, 2H, CH₂N); 3.55–3.65 (m, 0.5H,

CHN); 3.65–3.80 (m, 0.5H, CHN); 5.13 (s, 0.5+0.5H)

and 5.15 (s, 0.5+0.5H) (CH₂Ph); 7.30–7.45 (m, 5H,

aromatics). Anal. (C₁₄H₁₇NO₃): C, H, N.

1

(2R)-Phenylmethyl 2-oxiran-2-ylpyrrolidine-1-carboxy-

late [(2R)-10]. Using the same procedure described for

(2S)-10, and starting from 1.5 g (6.5 mmol) of R-(+)-5

and 2.25 g (13.0 mmol) of m-chloroperbenzoic acid

(mCPBA), 1.41 g (5.66 mmol, 86.5% yield) of (2R)-10

were obtained as a mixture of two diastereoisomers.

IR (neat) n (cm^À1): 3600–3200 (OH); 1690 (C¼O), H

NMR (CDCl₃) d (ppm): 1.60–2.05 (m, 4H, CH₂CH₂);

2.40–2.80 (m, 2H, CH₂S); 3.25–4.15 (m, 4H,

CH₂N+CHO+CHN); 5.12 (s, 2H, CH₂Ph); 6.40–6.70

(bs, 2H, OH+SH); 7.30–7.45 (m, 5H, aromatics). Anal.

(C₁₄H₁₉NO₃S): C, H, N.

D

½a₂₀=+15.8^ꢀ(benzene), H NMR (CDCl₃) d (ppm):

1.80–2.10 (m, 4H, CH₂CH₂); 2.45–3.10 (m, 3H, CHCH₂

epoxide); 3.36–3.55 (m, 2H, CH₂N); 3.55–3.66 (m, 0.5H,

CHN); 3.66–3.80 (m, 0.5H, CHN); 5.12 (s, 0.5+0.5H)

(2S)-Phenylmethyl 2-(2-methyl-1,3-oxathiolan-5-yl)pyrro-

lidine-1-carboxylate [(2S)-13]. To a solution of 910 mg

(3.3 mmol) of (2S)-12 in 18.3mL of 2-propanol, 90 mg

(0.5 mmol) of p-toluensulfonic acid monohydrate were

1

3162

S. Dei et al. / Bioorg. Med. Chem. 11 (2003) 3153–3164

added. To this solution, 2.7 mL (25.5 mmol) of acetal-

dehyde dimethyl acetal were added, and the mixture was

kept to reﬂux for 2 h and concentrated in vacuo. The

residue was dissolved in 45 mL of diethyl ether, and the

organic layer was washed with 30 mL of water and dried

over Na₂SO₄. Evaporation of the solvent gave an oily

residue that was puriﬁed by column chromatography on

Al₂O₃(eluent: CH₂Cl₂/petroleum ether, 6:4). Yield

520 mg (1.7 mmol, 52%) of (2S)-13.

2.58 (m, 1H, CH_EN), 2.75–2.83(m, 1H, CH H_DS), 2.96–

3.20 (m, 2H, CH_CHS and CH_FHN), 3.80–3.92 (m, 1H,

OCH_B), 5.23(q, J=5.5 Hz, 1H, CHCH₃).

Each isomeric amine was transformed in the corres-

ponding oxalate by treatment with one equivalent of

oxalic acid in ethyl acetate (Table 3).

(2R, 5⁰R, 2⁰R)-1-Methyl-2-(2-methyl-1,3-oxathiolan-5-

yl)pyrrolidine [(+)-14a] and (2R, 5⁰S, 2⁰S)-1-methyl-2-

(2-methyl - 1,3 - oxathiolan - 5 - yl)pyrrolidine [(+)-14c].

Using the same procedure described for (2S)-14, and

starting from 650 mg (2.1mmol) of (2R)-13 and 500 mg

(13.2 mmol) of LiAlH₄, crude (2R)-14 was obtained. The

chromatographic separation on Al₂O₃(eluent CHCl₃/

petroleum ether 3:7) aﬀorded 100 mg of the ﬁrst isomer a,

70mg of the isomer c and another fraction of unidentiﬁed

½a^D₂₀=À67.0^ꢀ(CH₂Cl₂), ¹H NMR (CDCl₃) d (ppm):

1.56 (d, J=5.5 Hz, 3H, CH₃CH); 1.75–2.18 (m, 4H,

CH₂CH₂); 2.80–3.20 (m, 2H, CH₂S); 3.40–3.60 (m, 2H,

CH₂N); 4.02–4.47 (m, 2H, CHO+CHN); 5.00–5.25 (m,

3H, CH₂Ph+CHCH₃); 7.30–7.45 (m, 5H, aromatics).

Anal. (C₁₆H₂₁NO₃S): C, H, N.

(2R)-Phenylmethyl 2-(2-methyl-1,3-oxathiolan-5-yl)pyr-

rolidine-1-carboxylate [(2R)-13]. Using the same proce-

dure described for (2S)-13, and starting from 1.27 g

(4.5 mmol) of (2R)-12 and 3.81 mL (36.0 mmol) of acet-

aldehyde dimethyl acetal, crude (2R)-13 was obtained,

that was puriﬁed by column chromatography on Al₂O₃

(eluent: CH₂Cl₂/petroleum ether 6:4), aﬀording 650 mg

(2.1 mmol, 47% yield) of title compound as a mixture of

diastereoisomers.

isomers (fraction b). Total yield 56%. Anal. (C₉H₁₇NOS):

D

C, H, N. Elemental analysis and ½a of each isomer are

20

reported in Table 3. Hydrogens are deﬁned in Table 1.

(+)-14a. ¹H NMR (CDCl₃) d (ppm): 1.57 (d,

J=5.5 Hz, 3H, CH₃CH); 1.66–1.94 (m, 4H, CH₂CH₂);

2.20–2.29 (m, 1H, CHH_GN), 2.42 (s, 3H, CH₃N), 2.43–

2.51 (m, 1H, CH_EN), 2.83–2.92 (m, 1H, CHH_DS), 2.96–

3.15 (m, 2H, CH_CHS and CH_FHN), 3.94–4.03 (m, 1H,

OCH_B), 5.22 (q, J=5.5 Hz, 1H, CHCH₃); ¹³C NMR

(CDCl₃) d (ppm): 22.19 (q), 23.76 (t), 26.34 (t), 35.72 (t),

42.08 (q), 58.30 (t), 67.19 (d), 82.25 (d), 84.32 (d).

½a^D₂₀=+68.2^ꢀ(CH₂Cl₂), ¹H NMR (CDCl₃) d (ppm):

1.55 (d, J=5.5 Hz, 3H, CH₃CH); 1.74–2.16 (m, 4H,

CH₂CH₂); 2.80–3.20 (m, 2H, CH₂S); 3.35–3.70 (m, 2H,

CH₂N); 4.02–4.47 (m, 2H, CHO+CHN); 5.08–5.20 (m,

3H, CH₂Ph+CHCH₃); 7.30–7.45 (m, 5H, aromatics).

Anal. (C₁₆H₂₁NO₃S): C, H, N.

(+)-14c. ¹H NMR (CDCl₃) d (ppm): 1.59 (d,

J=5.7 Hz, 3H, CH₃CH); 1.55–2.00 (m, 4H, CH₂CH₂);

2.25–2.34 (m, 1H, CHH_GN), 2.52 (s, 3H, CH₃N), 2.45–

2.58 (m, 1H, CH_EN), 2.75–2.84 (m, 1H, CHH_DS), 2.95–

3.20 (m, 2H, CH_CHS and CH_FHN), 3.89–4.07 (m, 1H,

OCH_B), 5.24 (q, J=5.7 Hz, 1H, CHCH₃); ¹³C NMR

(CDCl₃) d (ppm): 22.06 (q), 23.90 (t), 28.22 (t), 36.19 (t),

42.86 (q), 58.45 (t), 67.91 (d), 82.76 (d), 87.76 (d).

(2S, 5⁰S, 2⁰S)-1-Methyl-2-(2-methyl-1,3-oxathiolan-5-yl)-

pyrrolidine [(À)-14a] and (2S, 5⁰R, 2⁰R)-1-methyl-2-(2-

methyl-1,3-oxathiolan-5-yl)pyrrolidine [(À)-14c]. A solu-

tion of 520 mg (1.7 mmol) of (2S)-13 dissolved in the

minimum amount of anhyd THF was added dropwise

to a suspension of 410 mg (10.8 mmol) of LiAlH₄in an.

THF at À18 ^ꢀC under nitrogen. The mixture was

allowed to reach room temperature, and after 4 h was

treated with brine and extracted with ethyl acetate. The

organic layer was dried over Na₂SO₄and concentrated

in vacuo to aﬀord an oily mixture of diastereoisomers

[(2S)-14]. The chromatographic separation on Al₂O₃

(eluent CHCl₃/petroleum ether 3:7) yielded 70 mg of

isomer a, 40 mg of the isomer c and another fraction of

Each isomer was transformed in the corresponding

oxalate by treatment with one equivalent of oxalic acid

in ethyl acetate (Table 3).

General procedure for the synthesis of the methiodides

An anhyd ether solution of the suitable tertiary amine

was treated with an excess of methyl iodide and kept for

1 night at rt in the dark. The obtained solid was ﬁltered,

dried under vacuum, and recrystallized (when neces-

sary) from absolute ethanol. Compounds (À)-9 a, c,

(+)-9 a, c, (À)-15 a, c, (+)-15 a, c have been prepared

by this procedure. The chemical and physical char-

acteristics of the compounds are reported in Table 4.

Their ¹H NMR spectra are consistent with the proposed

structures. The spectrum of (+)-9a is reported as an

example: ¹H NMR (CDCl₃) d (ppm): 1.42 (d, 3H,

CH₃CH, J=4.8 Hz); 2.05–2.45 (m, 4H, CH₂CH₂); 3.32

(s, 3H, CH₃N); 3.55 (s, 3H, CH₃N); 3.63–4.00 (m, 3H,

CHHO+CHHN+ CHN); 4.10–4.22 (m, 1H, CHHO);

4.59–4.74 (m, 1H, CHHN); 4.70–4.74 (m, 1H,

OCHCH₂); 5.05 (q, 1H, OCHCH₃, J=4.8 Hz).

unidentiﬁed isomers (fraction b). Total yield 41%. Ele-

D

mental analysis and ½a of each isomer are reported in

20

Table 3. Hydrogens are deﬁned in Table 1.

(À)-14a. ¹H NMR (CDCl₃) d (ppm): 1.58 (d,

J=5.5 Hz, 3H, CH₃CH); 1.66–1.96 (m, 4H, CH₂CH₂);

2.19–2.30 (m, 1H, CHH_GN), 2.41 (s, 3H, CH₃N), 2.43–

2.51 (m, 1H, CH_EN), 2.84–2.92 (m, 1H, CHH_DS), 2.97–

3.15 (m, 2H, CH_CHS and CH_FHN), 3.95–4.03 (m, 1H,

OCH_B), 5.22 (q, J=5.5 Hz, 1H, CHCH₃).

(À)-14c. ¹H NMR (CDCl₃) d (ppm): 1.58 (d,

J=5.5 Hz, 3H, CH₃CH); 1.56–2.00 (m, 4H, CH₂CH₂);

2.23–2.34 (m, 1H, CHH_GN), 2.51 (s, 3H, CH₃N), 2.45–

S. Dei et al. / Bioorg. Med. Chem. 11 (2003) 3153–3164

3163

Crystal structure determination and reﬁnement of (+)-

15a. Diﬀraction data were collected at 293K on a Sie-

mens P4 Four circle diﬀractometer equipped with a

graphite-monochromated CuK_aradiation, using a y/2y

scan technique.

the asymmetric unit were disordered and were modelled

as two diﬀerent positions. Reﬁnement of the Flack para-

meter [À0.0154 (0.0100)] conﬁrmed that the right-handed

diastereoisomer had been obtained in our initial structure

determination. Least square superposition of the four

independent molecules led to an average rms of 0.24A.

The crystal data and details of the data collection and

structure reﬁnement are summarised in Table 5. During

the data collection three standard reﬂections were mea-

sured every four hundred reﬂections collected as orien-

tation and intensity control; signiﬁcant intensity decay

was not observed. Corrections for Lorentz and polar-

isation eﬀects and for absorption by ꢀ-scans were

applied. The crystal structure was solved by direct

methods using the SIR97 program²⁹which gave the

position of most of the non-hydrogen atoms. The

remaining atoms were identiﬁed by successive Fourier

diﬀerence syntheses. Four identical independent com-

pound molecules and two water molecules were found

in the asymmetric unit. Reﬁnement was carried out on

F²by full-matrix least square techniques, using the

SHELX97 program package.³⁰Hydrogen atoms were

added in the model constrained to idealised positions

and reﬁned using a riding model with riding isotropic

displacement parameters. Hydrogen atoms of the sol-

vent water molecules were not added. All the non-

hydrogen atoms were reﬁned anisotropically. Atoms

C5, C6, C7 in one of the four independent molecules in

In Figure 1 (see above) an ORTEP representation of

(+)-15a showing one of the four independent molecules

is shown. A complete set of data has been deposited at

the Cambridge Crystallographic Data Center with

number CCDC 185530.

Pharmacology

Binding studies. Membrane preparation. Male rats (Wis-

tar, 200 g) were killed by decapitation and the brains

were removed and immediately placed on ice. The brain

was dissected, homogenised in 10vol 0.32M sucrose with

a glass–teﬂon homogeniser. The homogenate was then

centrifuged at 1000g for 15min; the resulting supernatant

was further centrifuged at 17,000g for 20min and the pel-

let was stored at À80^ꢀC until assayed.³¹

Binding experiments. The muscarinic receptors were

labelled with 0.1 nM [³H]N-methyl scopolamine

([³H]NMS, 79.5 Ci/mmol from NEN-Dupont). The fro-

zen pellet was suspended in Krebs–Hepes buﬀer pH 7.4

(composition, mM: NaCl 118, KCl 4.7, NaHCO₃5,

KH₂PO₄1.2, glucose 11, MgSO₄1.2, CaCl₂2.5 and

Hepes 20), at 4 ^ꢀC as previously described in Freedman

et al.³¹Aliquots of cerebral membranes at a protein

concentration of 100–150 mg/mL were incubated at

30 ^ꢀC for 60 min in a ﬁnal volume of 1 mL with the

marker ligand and with diﬀerent concentrations of

unlabeled ligands (0.1 nM–0.1 mM); the incubation was

terminated by ﬁltration through Whatman GF/B glass

ﬁber ﬁlters presoaked in 0.1% polyethyleneimine (PEI),

using a Brandel M-48R 48-well cell harvester. Filters

were washed twice with 10 mL of ice-cold 0.9% saline

solution. Protein concentration was estimated using the

Pierce protein assay reagent (Pierce ChemicalCo.,

Rockford, IL, USA) based on the method of Bradford³²

with bovine serum albumin as standard. In all experi-

ments, the radioactivity retained by ﬁlters was measured

in a liquid scintillation counter (TRI-CARB 1900TR,

Packard) after the addition of 4 mL of scintillation ﬂuid

(Filter Count, Packard) and all measurements were

obtained in duplicate. The binding data were evaluated

quantitatively with non-linear least-square curve ﬁttings

using the computer programs ALLFIT³³and LIGAND.³⁴

Table 4. Chemical and physical characteristics of derivatives 9 and 15

D

20

Compd

Stereochemistry

Mp (^ꢀC)

½ꢀ

Analysis

(À)-9a

2S,4⁰S, 2⁰R

2S,4⁰R, 2⁰S

2R,4⁰R, 2⁰S

2R,4⁰S, 2⁰R

2S,5⁰S, 2⁰S

2S,5⁰R, 2⁰R

2R,5⁰R, 2⁰R

2R,5⁰S, 2⁰S

177–180

107–108

180–182

105–106

145–147

148–150

148–151

151–152

À32.5^a

+26.5^b

+6.0^a

À41.5^a

À12.2^b

+42.2^a

+13.8^a

C₁₀H₂₀NJO₂

C₁₀H₂₀NJOS

(À)-9c

À5.6^a

(+)-9a

(+)-9c

(À)-15a

(À)-15c

(+)-15a

(+)-15c

^aIn CHCl₃.

^bIn MeOH.

Table 5. Crystal data and structure reﬁnement for (+)-15a

Formula

C₄₀H₈₀I₄N₄O₆S₄

1348.92

P 2₁

Formula weight

Space group

Unit cell dimensions

a (A)

14.4350(19)

7.8400(11)

25.503(3)

99.637(9)

2845.5(7)

8

1.574

18.90

CuK_a

1.76–64.52

6456

5702

95.4

b (A)

c (A)

b (^ꢀ)

Volume (A³)

Z

Density (calcd) (g/cm³)

Abs coeﬀ (mm^À1

Radiation

)

Functional in vitro tests. Guinea-pig ileum. Male guinea

pigs (200–300 g) were killed by cervical dislocation.

Two-centimeter-long portions of terminal ileum were

taken at about 5 cm from the ileum–cecum junction and

mounted under 1 g of tension in 20-mL organ baths

containing physiological salt solution [PSS; composition

(mM): NaCl 118, NaHCO₃23.8, KCl 4.7, MgSO₄.7H₂O

1.18, KH₂PO₄1.18, CaCl₂2.52, and glucose 11.7] at

37 ^ꢀC and aerated with 5% CO₂–95% O₂. Tension

changes were recorded isotonically by means of a force–

Theta range for data collection (^ꢀ)

Reﬂns collected

No. of unique reﬂns

Completeness to theta=64.52^ꢀ(%)

Value of R_int

0.043

Final R indices [I>2s(I)]

R indices (all data)

Absolute struct param

Extinction coeﬀ

Largest diﬀ. peak and hole (e A^À3

R1=0.0589, wR2=0.1630

R1=0.0659, wR2=0.1736

À0.014(10)

0.00202(16)

)

1.848 and À1.400

3164

S. Dei et al. / Bioorg. Med. Chem. 11 (2003) 3153–3164

displacement transducer connected to the MacLab sys-

tem PowerLab/800 and to a two-channel Gemini poly-

graph (U. Basile). Tissues were equilibrated for 30 min

and dose–response curves for arecaidine propargyl ester

(APE) were obtained at 30-min intervals, the ﬁrst one

being discarded and the second one being taken as the

control. The concentration of agonist in the organ bath

was increased approximately 3-fold at each step, with

each addition being made only after the response to the

previous addition had attained a maximal level and

remained steady. Following 30 min of washing, a new

dose–response curve for the agonist under study was

obtained. Responses were expressed as a percentage of

the maximal response obtained in the control curve. The

results are expressed in terms of Àlog ED₅₀, the con-

centration of agonist required to produce 50% of the

maximum contraction. Parallel experiments in which

tissues received only the reference agonist were run in

order to check any variation in sensitivity.

Pigini, M.; Cingolani, M. L.; Gamba, G.; Leone, L.; Pigini, P.;

Re, L. Eur. J. Med. Chem. 1978, 13, 357.

10. Teodori, E.; Gualtieri, F.; Angeli, P.; Brasili, L.; Gian-

nella, M.; Pigini, M. J. Med. Chem. 1986, 29, 1610.

11. Triggle, D. J. In ChemicalPharmacoolgy of the Synapse

;

Triggle, D.J., Triggle, C,.R., Eds.; Academic: New York,

1976; p 291.

12. Pigini, M.; Brasili, L.; Giannella, M.; Gualtieri, F. Eur. J.

Med. Chem. 1981, 16, 415.

13. Belleau, B.; Puranen, J. J. Med. Chem. 1963, 6, 325.

14. Wunsch, E.; Graf, W.; Keller, O.; Keller, W.; Wersin, G.

Synthesis 1986, 958.

15. Almeida, M. L. S.; Grehn, L.; Ragnarsson, U. J. Chem.

Soc., Perkin Trans. 1 1988, 1905.

16. Cassal, J.-M.; Furst, A.; Meier, W. Helv. Chim. Acta 1976,

59, 1917.

17. Mazzini, C.; Sambri, L.; Regeling, H.; Zwanenburg, B.;

Chittenden, G. J. F. J. Chem. Soc., Perkin Trans. 1 1997, 3351.

18. Ito, A.; Takahashi, R.; Baba, Y. Chem. Pharm. Bull. 1975,

23, 3081.

19. Hamada, Y.; Shioiri, T. Chem. Pharm. Bull. 1982, 30, 1921.

20. Mori, M.; Kanda, N.; Oda, I.; Ban, Y. Tetrahedron 1985,

41, 5465.

21. Seijas, J. A.; Vazquez-Tato, M. P.; Castedo, L.; Estevez,

R. J.; Onega, M. G.; Ruiz, M. Tetrahedron 1992, 48, 1637.

22. Parikh, J. R.; Doering, W. v. E. J. Am. Chem. Soc. 1967,

89, 5505.

23. Akashi, K.; Palermo, R. E.; Sharpless, K. B. J. Org.

Chem. 1978, 43, 2063.

24. Thurkauf, A.; Mattson, M. V.; Richardson, S.; Mirsade-

ghi, S.; Ornstein, P. L.; Harrison, E. A.; Rice, K. C.; Jacobson,

A. E.; Monn, J. A. J. Med. Chem. 1992, 35, 1323.

25. Mizuno, A.; Hamada, Y.; Shioiri, T. Synthesis 1980, 12, 1007.

26. Hirsch, J. A.; Truc, V. C. J. Org. Chem. 1986, 51, 2218.

27. Hulme, E. C.; Lu, Z.-L.; Bee, M.; Curtis, C. A. M.; Sal-

danha, J. Life Sci. 2001, 68, 2495.

Acknowledgements

This research was supported by funds of the Italian

Ministry of University and Scientiﬁc Research

(MURST). We are grateful to Dr. Katia Varani (Uni-

versity of Ferrara) who performed the nicotinic binding

experiments.

References and Notes

1. Caulﬁeld, M. P. Pharma. Ther. 1993, 58, 319.

2. Chavez-Noriega, L. E.; Crona, J. H.; Washburn, M. S.;

Urrutia, A.; Elliott, K. J.; Johnson, E. C. J. Pharmacol. Exp.

Ther. 1997, 280, 346.

3. Gualtieri, F. In Receptor Chemistry Towards the Third

Millennium; Gulini, U., Giannella, M., Quaglia, W., Marucci,

G., Eds.; Elsevier Science: Amsterdam, 2000; p 85.

4. Bartus, R. T. Exp. Neurol. 2000, 163, 495.

5. Korczyn, A. D. Exp. Opin. Invest. Drugs 2000, 9, 2259.

6. Schmitt, J. D.; Bencherif, M. Ann. Rep. Med. Chem. 2000,

35, 41.

28. Shi, L.; Javitch, J. A. Ann. Rev. Pharmacol. Toxicol. 2002,

42, 437.

29. Altomare, A.; Burla, M. C.; Camalli, M.; Cascarano,

G. L.; Giacovazzo, C.; Guagliardi, A.; Moliterni, A. G. G.;

Polidori, G.; Spagna, R. J. Appl. Cryst. 1999, 32, 115.

30. Sheldrick, G. M. SHELX97; Institut fur Anorganische

Chemie: Gottingen, Germany.

31. Freedman, S. B.; Harley, E. A.; Iversen, L. L. Br. J.

Pharmacol. 1988, 93, 437.

32. Bradford, M. M. Anal. Biochem. 1976, 72, 248.

33. De Lean, A.; Munson, P. J.; Rodbard, D. Am. J. Physiol.

1978, 235, E97.

7. Clementi, F.; Fornasari, D.; Gotti, C. Eur. J. Pharmacol.

2000, 393, 3 .

8. Angeli, P. IlFarmaco 1995, 50, 565.

34. Munson, P. J.; Rodbard, D. Anal. Biochem. 1980, 107,

220.

9. Melchiorre, C.; Angeli, P.; Giannella, M.; Gualtieri, F.;

Article Doi

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

DOI: 10.1016/S0968-0896(03)00236-0

Source and publish data:

Authors:

Article abstract of DOI:10.1016/S0968-0896(03)00236-0

Full text of DOI:10.1016/S0968-0896(03)00236-0

Products guided by the article

R&D Labs maybe for 623938-57-8

Relevant to this article

Hot Product