Stereoselective synthesis of 1,2-diamino-1,2-diarylethane derivatives

Article abstract of DOI:10.1007/s11172-005-0238-z

A procedure was developed for selective opening of the cis-2,4,5- triarylimidazoline ring to form erythro-1,2-diamino-1,2-diarylethane derivatives. These ring-opening products, erythro-ethylenediamine derivatives, can undergo quantitative isomerization to

Full text of DOI:10.1007/s11172-005-0238-z

Russian Chemical Bulletin, International Edition, Vol. 54, No. 1, pp. 211—214, January, 2005
211
Stereoselective synthesis of 1,2ꢀdiaminoꢀ1,2ꢀdiarylethane derivatives
ꢀ
I. V. Bessonov, N. A. Lozinskaya, V. R. Katashova, M. V. Proskurnina, and N. S. Zefirov
Department of Chemistry, M. V. Lomonosov Moscow State University,
1 Leninskie Gory, 119992 Moscow, Russian Federation.
Fax: +7 (095) 939 0290. Eꢀmail: natalylozinskaya@mail.ru
A procedure was developed for selective opening of the cisꢀ2,4,5ꢀtriarylimidazoline ring
to form erythroꢀ1,2ꢀdiaminoꢀ1,2ꢀdiarylethane derivatives. These ringꢀopening products,
erythroꢀethylenediamine derivatives, can undergo quantitative isomerization to threoꢀethyleneꢀ
diamine derivatives in the presence of strong bases in DMSO.
Key words: vicinal diamines; stereoselective synthesis; isomerization; cisꢀimidazolines.
Scheme 1
The design of catalysts providing higher stereoselecꢀ
tivity of reactions is a promising field of modern organic
chemistry. For this purpose, researchers are carrying out
an extensive search for new complexꢀforming ligands,
which are rather sterically crowded and can easily be modiꢀ
fied. From this point of view, 1,2ꢀethylenediamine deꢀ
rivatives are of considerable interest. However, the range
of vicinal diamines is presently limited to 1,2ꢀdiphenylꢀ
ethyleneꢀ1,2ꢀdiamine, 1,2ꢀdiaminocyclohexane, and their
derivatives. The reason is that a simple procedure has
been devised in detail only for the synthesis of these comꢀ
pounds, whereas a convenient and universal method for
the synthesis of vicinal diamines is lacking. The developꢀ
ment of a simple and stereoselective procedure for the
synthesis of 1,2ꢀdiamines, which would allow one to perꢀ
form successive modifications of each amino group, could
substantially facilitate the solution of many synthetic
problems.
As part of our continuing studies aimed at devising a
method for the synthesis of 1,2ꢀdiarylethylenediamines,1,2
we examined the possibility of ring opening in cisꢀ and
transꢀimidazolines to produce derivatives of vicinal diꢀ
amines. One can easily and stereoselectively prepare
cisꢀ and transꢀimidazolines 1 and 2 from the correspondꢀ
ing aromatic aldehydes 3 and ammonia (Scheme 1).2
The ring closure in the anion derived from aldehyde
ammonia 4 occurs strictly disrotatory in accordance
with electronic control over the reaction. However,
transꢀimidazolines containing electronꢀwithdrawing subꢀ
stituents in the aromatic ring are difficult to synthesize,
because such imidazolines undergo predominantly oxidaꢀ
tion to the corresponding imidazoles 5 (Scheme 1).
The 2,4,5ꢀtriarylimidazoline ring opening is a more
complicated problem than the opening of rings containꢀ
ing aliphatic substituents because the former ring is more
inert due, apparently, to conjugation of the C=N double
bond with the aryl group. For example, refluxing of
i. ButOK/THF, –10 °C, 1—10 min. ii. ButOK/ButOH, 60 °C.
2ꢀmethylꢀ4,5ꢀtetramethyleneimidazoline in aqueous alꢀ
cohol is sufficient to perform ring opening (Scheme 2),3
whereas the 2,4,5ꢀtriarylimidazoline ring opening requires
more drastic conditions, such as refluxing with acetic anꢀ
hydride giving rise to NꢀacetylꢀN´ꢀaroylꢀsubstituted viciꢀ
nal diamine4,5 or reduction with aluminum amalgam to
form unsubstituted diamine.6
Scheme 2
Earlier,1 we have studied the reactions of aromatic
aldehydes with ammonium acetate yielding N´ꢀaroylꢀ
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 1, pp. 206—209, January, 2005.
1066ꢀ5285/05/5401ꢀ0211 © 2005 Springer Science+Business Media, Inc.

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Bessonov et al.
Table 1. Reactions of imidazolines 1 with aldehydes*
Nꢀarylidene derivatives 6 (Scheme 3), which should proꢀ
ceed through the formation of cisꢀimidazoline.
Ar
RCHO
Yield of product 6
(%)
Scheme 3
Ph
PhCHO
98 (6a)
76 (6b)
80 (6c)
87 (6d)
91 (6e)
76 (6f)
87 (6g)
—
4ꢀMeO—C6H4
3ꢀNO2—C6H4
Ph
Ph
4ꢀMeO—C6H4CHO
3ꢀNO2—C6H4CHO
4ꢀBrC6H4CHO
4ꢀMeOC6H4CHO
2ꢀHOC6H4CHO
PhCHO
Paraformaldehyde
nꢀPropanal
3ꢀNO2—C6H4CHO
Ph
4ꢀMeOC6H4
Ph
Ph
4ꢀButC6H4
**
76 (6h)
Ar = Ph, 2ꢀthienyl, 4ꢀClC6H4, 4ꢀBrC6H4, 4ꢀFC6H4, 3ꢀNO2C6H4
In the present study, we found that cisꢀimidazolines
can react with aromatic aldehydes in the presence of
catalytic amounts of acetic acid to give derivatives 6
(Scheme 4). It is of fundamental importance that
transꢀ2,4,5ꢀtriarylimidazolines are not involved in this reꢀ
action.
* Dioxane, AcOH catal., ∆.
** Traces of a mixture containing NꢀbenzoylꢀN´ꢀpropylideneꢀ
1,2ꢀdiaminoꢀ1,2ꢀdiphenylethane, which we failed to separate
from byꢀproducts.
the ring more readily react with cisꢀimidazolines (the reꢀ
action time decreases). An attempt to use aliphatic aldeꢀ
hydes for the imidazoline ring opening failed (Table 1).
This scheme has advantages over many other methods
because it provides a way of removing symmetry of vicinal
diamines due to the presence of differently protected
amino groups. Each amino group can be independently
modified by successive hydrolysis. In addition, due to the
fact that transꢀimidazolines are not involved in this reacꢀ
tion, the method can be used to separate a mixture of
cisꢀ and transꢀ2,4,5ꢀtriarylimidazolines.
Scheme 4
We also demonstrated for the first time that erythro
compound 6a can undergo quantitative isomerization to
threo compound 7a in the presence of strong bases (such
as NaH, ButOK) in DMSO. This substantially extends
the synthetic scope of the reaction because it allows one
i. RCHO, dioxane, AcOH, ∆.
6
Ar
R
a
b
c
d
e
f
Ph
4ꢀMeO—C6H4
3ꢀNO2—C6H4
Ph
Ph
4ꢀMeO—C6H4
3ꢀNO2—C6H4
4ꢀBr—C6H4
4ꢀMeOꢀC6H4
2ꢀOH—C6H4
Ph
Scheme 5
Ph
Ph
g
h
4ꢀMeO—C6H4
But—C6H4
3ꢀNO2—C6H4
We found the optimal conditions for this reaction.
The highest yield was obtained with the use of either
DMF or dioxane as the solvent. However, dioxane makes
isolation of the product easier. The reactions with the use
of other solvents, such as THF, dichloromethane, alcoꢀ
hol, toluene, or xylene, afford products in substantially
lower yields and require longer time. We also found that
mineral acids, viz., HCl or H2SO4, do not catalyze this
reaction, whereas the presence of catalytic amounts of
acetic or trifluoroacetic acids (the molar ratio imidazoꢀ
line : AcOH = 5 : 1) leads to a decrease in the reaction
time. In the presence of a stoichiometric amount of the
acid, the reaction is completely suppressed. Aromatic alꢀ
dehydes containing electronꢀwithdrawing substituents in
Substituents
a
Ph
b
c
4ꢀMeO—C6H4
3ꢀNO2—C6H4

1,2ꢀDiaminoꢀ1,2ꢀdiarylethane derivatives
Russ.Chem.Bull., Int.Ed., Vol. 54, No. 1, January, 2005
213
(3.2 mmol, 98%), m.p. 257 °C. 1H NMR (300.13 MHz,
DMSOꢀd6), δ: 4.80 (d, 1 H, CH—N=, J1 = J2 = 8 Hz); 5.65 (dd,
1 H, CH—NH, J1 = J2 = 8 Hz); 7.05—7.70 (m, 20 H); 8.00 (s,
1 H, CH=N); 8.80 (d, 1 H, NH, J = 8 Hz). Found (%): C, 83.01;
H, 5.91; N, 6.72. C28H24N2O. Calculated (%): C, 83.14; H, 5.98;
N, 6.93.
to obviate the synthesis of transꢀimidazolines, which ofꢀ
ten involves problems associated with the preparation of
threo derivatives of vicinal diamines.
It appeared that the presence of the arylidene fragꢀ
ment is necessary for isomerization to occur. For exꢀ
ample, isomerization of monoacylated and completely
acylated cisꢀdiamine, which was prepared by the reaction
of 3a with acetic anhydride,4 did not occur (Scheme 6).
erythroꢀNꢀ(4ꢀMethoxybenzoyl)ꢀN´ꢀ(4ꢀmethoxypheꢀ
nyl)methylideneꢀ1,2ꢀdiaminoꢀ1,2ꢀdi(4ꢀmethoxyphenyl)ethane
(6b). Refluxing of a mixture of cisꢀ2,4,5ꢀtri(4ꢀmethoxypheꢀ
nyl)imidazoline (1b) (1 g, 2.5 mmol) and anisaldehyde (0.5 g,
4.7 mmol) for 24 h produced compound 6b in a yield of 1 g
(1.9 mmol, 76%), m.p. 218 °C. 1H NMR (300.13 MHz,
DMSOꢀd6), δ: 3.69 and 3.70 (both s, 3 H each, OMe); 3.80 (s,
6 H, OMe); 4.66 (d, 1 H, CH—N=, J = 8 Hz); 5.45 (dd, 1 H,
CH—NH, J1 = J2 = 8 Hz); 6.70—6.90 (m, 8 H); 7.35, 7.45,
7.55, and 7.65 (all d, 2 H each); 7.90 (s, 1 H, CH=N); 8.19 (d,
1 H, NH, J = 8 Hz). Found (%): C, 73.30; H, 5.99; N, 5.28.
C32H32N2O5., Calculated (%): C, 73.26; H, 6.15; N, 5.34.
erythroꢀNꢀ(3ꢀNitrobenzoyl)ꢀN´ꢀ(3ꢀnitrophenyl)methylideneꢀ
1,2ꢀdiaminoꢀ1,2ꢀdi(3ꢀnitrophenyl)ethane (6c). Refluxing of a
mixture of cisꢀ2,4,5ꢀtri(3ꢀnitrophenyl)imidazoline (1c) (4 g,
9.2 mmol) and 3ꢀnitrobenzaldehyde (1.4 g, 9.2 mmol) for 7 h
afforded compound 6c in a yield of 4.2 g (7.2 mmol, 78%), m.p.
256 °C. 1H NMR (400.13 MHz, 25.6 °C, DMSOꢀd6), δ: 5.14 (d,
1 H, CH—N=, J = 9.6 Hz); 5.86 (dd, 1 H, CH—NH, J =
9.4 Hz, J = 9.6 Hz); 7.52 (dd, 1 H, J = 7.8 Hz, J = 8.1 Hz); 7.67
(m, 2 H); 7.87 (m, 1 H); 8.11 (m, 5 H); 8.26 (m, 2 H); 8.33
(m, 1 H); 8.49 (s, 2 H); 8.57 and 8.60 (both s, 1 H each); 9.53
(d, 1 H, NH, J = 9.4 Hz).
erythroꢀNꢀBenzoylꢀN´ꢀ(4ꢀbromophenyl)methylideneꢀ1,2ꢀ
diaminoꢀ1,2ꢀdiphenylethane (6d). Refluxing of a mixture of
cisꢀ2,4,5ꢀtriphenylimidazoline (1a) (1 g, 3.3 mmol) and
4ꢀbromobenzaldehyde (0.6 g, 3.3 mmol) for 18 h gave comꢀ
pound 6d in a yield of 1.4 g (2.9 mmol, 88%), m.p. 232—233 °C.
1H NMR (300.13 MHz, DMSOꢀd6), δ: 4.45 (d, 1 H, J = 5 Hz);
5.00 (dd, 1 H, J = 5 Hz, J = 5 Hz); 7.10—7.90 (m, 19 H);
8.00 (s, 1 H); 8.70 (d, 1 H, J = 7 Hz). Found (%): C, 69.68;
H, 4.83; N, 5.98. C28H23BrN2O. Calculated (%): C, 69.57;
H, 4.80; N, 5.80.
Scheme 6
The presence of electronꢀwithdrawing substituents in
the aromatic ring of compound 6 facilitates isomerizaꢀ
tion. For example, isomerization of a compound with
Ar = 3ꢀNO2ꢀC6H4 occurs in the presence of KOH in
DMSO, whereas isomerization of a compound with
4ꢀMeOꢀC6H4 takes place only in the presence of sodium
hydride.
Experimental
The reactions were monitored and the purities of the prodꢀ
ucts were checked by TLC on a fixed layer of silica gel (Silufol
plates). The NMR spectra were recorded on Bruker ACꢀ300,
Bruker ACꢀ200, and Varian VXRꢀ400 instruments. The chemiꢀ
cal shifts are given on the δ scale with respect to Me4Si as the
internal standard. The melting points were determined on a hotꢀ
stage apparatus in an open capillary tube. All melting points are
uncorrected. Elemental analysis was carried out on a CarloErba
CHNꢀanalyzer.
erythroꢀNꢀBenzoylꢀN´ꢀ(4ꢀmethoxyphenyl)methylideneꢀ1,2ꢀ
diaminoꢀ1,2ꢀdiphenylethane (6e). Refluxing of a mixture of
cisꢀ2,4,5ꢀtriphenylimidazoline (1a) (0.5 g, 1.65 mmol) and
4ꢀmethoxybenzaldehyde (0.2 g, 1.65 mmol) for 18 h afꢀ
forded compound 6e in a yield of 0.66 g (1.52 mmol, 92%), m.p.
1
210—215 °C. H NMR (300.13 MHz, DMSOꢀd6), δ: 3.90 (s,
3 H, MeO); 4.72 (d, 1 H, CH—N, J = 8.8 Hz); 5.45 (dd, 1 H,
CH—NH, J = 8.8 Hz, J = 8.8 Hz); 7.05 (d, 2 H, J = 8 Hz);
7.10—7.60 (m, 15 H); 7.80 (d, 2 H, J = 8 Hz); 7.90 (s, 1 H,
CH=N); 8.70 (d, 1 H, NH, J = 8 Hz). Found (%): C, 80.10;
H, 6.03; N, 6.40. C29H26N2O2. Calculated (%): C, 80.16;
H, 6.03; N, 6.45.
erythroꢀNꢀBenzoylꢀN´ꢀ(2ꢀhydroxyphenyl)methylideneꢀ1,2ꢀ
diaminoꢀ1,2ꢀdiphenylethane (6f). Refluxing of a mixture of
cisꢀ2,4,5ꢀtriphenylimidazoline (1a) (1 g, 3.3 mmol) and salicyꢀ
laldehyde (0.5 g, 4.0 mmol) for 18 h produced compound 6f in a
yield of 1 g (2.3 mmol, 72%), m.p. 248—250 °C. 1H NMR
(300.13 MHz, DMSOꢀd6), δ: 4.59 (d, 1 H, CH—N, J = 8.8 Hz);
5.70 (dd, 1 H, CH—NH, J1 = J2 = 8.8 Hz); 6.80—7.45 (m, 19 H);
7.90 (s, 1 H, CH=N); 8.70 (d, 1 H, NH, J = 8 Hz); 10.00 (br.s,
1 H, OH). Found (%): C, 79.70; H, 5.71; N, 6.85. C29H24N2O2.
Calculated (%): C, 79.98; H, 5.75; N, 6.66.
All solvents were purified and dehydrated according to stanꢀ
dard procedures.
Acidꢀcatalyzed imidazoline ring opening in aldehydes (general
procedure). Glacial acetic acid (0.1 mL) and aldehyde (3.3 mmol)
were added to a solution of imidazoline 1 (3.3 mmol) in dioxane
(20 mL). The resulting mixture was refluxed. The reaction was
monitored by TLC (ethyl acetate as the eluent). After compleꢀ
tion of the reaction, the solution was poured into water (100 mL).
The precipitate that formed was recrystallized from ethanol and
analyzed. This method was used to prepare compounds 6a—h.
erythroꢀNꢀBenzoylꢀN´ꢀphenylmethylideneꢀ1,2ꢀdiaminoꢀ1,2ꢀ
diphenylethane (6a). Refluxing of a mixture of cisꢀ2,4,5ꢀtriꢀ
phenylimidazoline (1a) (1 g, 3.3 mmol) and benzaldehyde (0.5 g,
4.7 mmol) for 18 h afforded product 6a in a yield of 1.3 g

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Bessonov et al.
erythroꢀNꢀ(4ꢀMethoxybenzoyl)ꢀN´ꢀphenylmethylideneꢀ1,2ꢀ
297 (8), 208 (100), 193 (10), 167 (13), 152 (10), 105 (75), 77
(47). Found (%): C, 83.01; H, 5.91; N, 6.72. C28H24N2O. Calꢀ
culated (%): C, 83.15; H, 5.97; N, 6.93.
diaminoꢀ1,2ꢀdi(4ꢀmethoxyphenyl)ethane (6g). Refluxing of a mixꢀ
ture of cisꢀ2,4,5ꢀtri(4ꢀmethoxyphenyl)imidazoline (1b) (1 g,
2.5 mmol) and benzaldehyde (0.5 g, 4.7 mmol) for 18 h afforded
compound 6g in a yield of 1.1 g (2.2 mmol, 87%), m.p. 215 °C.
1H NMR (300.13 MHz, DMSOꢀd6), δ: 3.69, 3.71, and 3.80 (all s,
3 H each, MeO); 4.70 (d, 1 H, CH—N, J = 8.8 Hz); 5.48 (dd,
1 H, CH—NH, J1 = J2 = 8.8 Hz); 7.70—7.90 (m, 6 H);
7.25—7.45 (m, 7 H); 7.65 (d, 4 H, J = 8 Hz); 8.00
(s, 1 H, CH=N); 8.15 (br.s, 1 H, NH). Found (%): 75.59;
H, 6.00; N, 5.99. C31H30N2O4. Calculated (%): C, 75.28;
H, 6.11; N, 5.66.
threoꢀNꢀ(4ꢀMethoxybenzoyl)ꢀN´ꢀ(4ꢀmethoxyphenyl)methylꢀ
ideneꢀ1,2ꢀdiaminoꢀ1,2ꢀdi(4ꢀmethoxyphenyl)ethane (7b). After
16 h, threo isomer 7b was synthesized from erythro isomer 6b
(2 g, 3.8 mmol) in a yield of 1.8 g (3.4 mmol, 90%), m.p. 212 °C.
1H NMR (399.95 MHz, DMSOꢀd6), δ: 3.36 and 3.66 (both s,
3 H each, OMe); 3.75 (s, 6 H, OMe); 5.10 (d, 1 H, CH—N=,
J = 8 Hz); 5.44 (dd, 1 H, CH—NH, J = 8 Hz, J = 8 Hz);
6.70—6.90 (m, 8 H); 7.40 and 7.50 (both d, 2 H each, J = 6 Hz);
7.66 (m, 4 H); 8.23 (s, 1 H, CH=N); 8.55 (d, 1 H, NH, J =
8 Hz). 13C NMR (100.61 ppm, DMSOꢀd6, T = 27 °C), δ: 59.39,
55.37, 55.76, 67.77, 113.38, 113.81, 127.44, 128.56, 129.38,
133.65, 134.83, 135.29, 158.44, 160.85, 161.88, 162.71, 165.15.
Found (%): C, 73.30; H, 5.99; N, 5.28. C32H32N2O5., Calcuꢀ
lated (%): C, 73.26; H, 6.15; N, 5.34.
threoꢀNꢀ(3ꢀNitrobenzoyl)ꢀN´ꢀ(3ꢀnitrophenyl)methylideneꢀ
1,2ꢀdiaminoꢀ1,2ꢀdiꢀ(3ꢀnitrophenyl)ethane (7c). After 30 min,
threo isomer 7c was prepared from erythro isomer 6c (1.5 g,
2.6 mmol) in a yield of 1.4 g (2.4 mmol, 93%), m.p. 285 °C.
1H NMR (399.95 MHz, DMSOꢀd6), δ: 5.12 (d, 1 H, CH—N=,
J = 9.23 Hz); 5.85 (dd, 1 H, CH—NH, J = 9.57 Hz, J =
9.57 Hz); 7.60—8.70 (m, 16 H); 9.03 (s, 1 H); 9.39 (d, 1 H, NH,
J = 8 Hz). Found (%): C, 57.51; H, 3.47; N, 14.33. C28H20N6O9.
Calculated (%): C, 57.54; H, 3.45; N, 14.38.
erythroꢀNꢀ(4ꢀtertꢀButylbenzoyl)ꢀN´ꢀ(3ꢀnitrophenyl)methylꢀ
ideneꢀ1,2ꢀdiaminoꢀ1,2ꢀdi(4ꢀtertꢀbutylphenyl)ethane (6h). Refluxꢀ
ing of a mixture of cisꢀ2,4,5ꢀtri(4ꢀtertꢀbutylphenyl)imidazoline
(1c) (4 g, 8.6 mmol) and 3ꢀnitrobenzaldehyde (1.3 g, 8.6 mmol)
for 16 h gave compound 6h in a yield of 4 g (6.5 mmol, 76%),
1
m.p. 199 °C. H NMR (400.13 MHz, DMSOꢀd6), δ: 1.60 (s,
9 H, But); 1.23 (s, 9 H, But); 1.26 (s, 9 H, But); 4.82 (d, 1 H,
CH—N, J = 10 Hz); 5.58 (dd, 1 H, CH—NH, J = 10 Hz, J =
10 Hz); 7.23—7.25 (d, 2 H, J = 8 Hz); 7.35—7.40 (m, 6 H);
7.51—7.54 (m, 4 H); 7.67 (dd, 1 H, 3ꢀNO2C6H4, J1 = J2
=
8 Hz); 7.99 (d, 1 H, 3ꢀNO2C6H4, J = 8 Hz); 8.09 (s, 1 H,
3ꢀNO2C6H4); 8.23 (d, 1 H, J = 8 Hz); 8.34 (s, 1 H, CH=N);
8.75 (d, 1 H, NH, J = 10 Hz). Found (%): C, 77.70; H, 7.70; N,
6.75. C40H43N3O3. Calculated (%): C, 77.76; H, 7.67; N, 6.80.
Isomerization of an erythroꢀNꢀaroylꢀN´ꢀarylidene derivatives
of vicinal diamines 6 to threo isomers 7 (general procedure). Anꢀ
hydrous DMSO (30 mL) was placed in a 100ꢀmL flask and then
iceꢀcooled NaH (2.4 mmol, a 60% suspension in oil) was added.
After 10 min, compound 6 (2.4 mmol) was added. The reaction
mixture gradually turned darkꢀcherry. The mixture was stirred
under argon at room temperature for 0.5—16 h, after which
water (100 mL) was added. The precipitate that formed was
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1
separated, washed with ethanol, and dried. The H NMR specꢀ
trum shows that compound 7 has no impurity of the starting
erythro isomer.
threoꢀNꢀBenzoylꢀN´ꢀphenylmethylideneꢀ1,2ꢀdiaminoꢀ1,2ꢀ
diphenylethane (7a). After 6 h, threo isomer 7a was prepared
from erythro isomer 6a (1.3 g, 3.2 mmol) in a yield of 1.3 g
(3.2 mmol, 98%), m.p. 210 °C. 1H NMR (399.95 MHz,
DMSOꢀd6), δ: 5.23 (d, 1 H, CH—N=, J = 9 Hz); 5.60 (dd, 1 H,
CH—NH, J = 9 Hz, J = 9 Hz); 7.10—7.70 (m, 20 H); 8.04 (s,
1 H, CH=N); 8.70 (d, 1 H, NH, J = 9 Hz). 13C NMR
(100.61 ppm, DMSOꢀd6, T = 28 °C), δ: 59.99, 68.68, 127.06,
127.25, 127.43, 127.58, 128.08, 128.45, 128.59, 129.96, 131.47,
135.23, 140.97, 142.33, 142.86, 164.25, 165.97. MS, m/z (%):
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Received November 19, 2004;
in revised form December 29, 2004