Reaction of unsaturated phosphonate monoesters with bromo- and?iodo(bis-collidine) hexafluorophosphates

Article abstract of DOI:10.1016/j.tet.2007.07.032

Reaction of unsaturated phosphonate monoesters with bromo- and iodo(bis-collidine) hexafluorophosphates are reported to lead to the formation of five- to seven-membered phostones by exo mode cyclizations. When the chains of the unsaturated phosphonate monoesters are substituted in α of the double bond by a dioxolane group endo mode cyclizations are observed. These cyclizations give rise to the formation of 1,2-oxaphosphepane-2-oxide and 1,2-oxaphosphocane-2-oxide.

Full text of DOI:10.1016/j.tet.2007.07.032

Tetrahedron 63 (2007) 10059–10066
Reaction of unsaturated phosphonate monoesters with
bromo- and iodo(bis-collidine) hexafluorophosphates
a,b,
ꢀ a,b
ꢀ
Virginie Andre, Hind Lahrache,a Sylvie Robina,b and Gerard Rousseau
*
a
´
Univ Paris-Sud, I.C.M.M.O.,UMR8182, Laboratoire de Syntheꢁse Organique et Methodologie,
Ba^t. 420, Orsay Cedex F-91405, France
bCNRS, UMR 8182, Orsay Cedex F-91405, France
Received 5 April 2007; revised 10 July 2007; accepted 12 July 2007
Available online 19 July 2007
Abstract—Reaction of unsaturated phosphonate monoesters with bromo- and iodo(bis-collidine) hexafluorophosphates are reported to lead
to the formation of five- to seven-membered phostones by exo mode cyclizations. When the chains of the unsaturated phosphonate monoesters
are substituted in a of the double bond by a dioxolane group endo mode cyclizations are observed. These cyclizations give rise to the formation
of 1,2-oxaphosphepane-2-oxide and 1,2-oxaphosphocane-2-oxide.
Ó 2007 Elsevier Ltd. All rights reserved.
1. Introduction
The aim of this report is to examine the behavior of unsatu-
rated phosphonate monoesters with iodo and bromo(bis-
collidine) hexafluorophosphates, to study the scope of these
cyclizations and apply them to the formation of phospho
sugar derivatives. The case of a,b-ethylenic phosphonates,
which lead to dephosphorylation reactions has been already
reported.7
We have previously reported that reaction of iodo- and bro-
mo(bis-collidine) hexafluorophosphates with u-ethylenic
acids allowed the formation of halo lactones of various
ring sizes.1 Reactions with the corresponding phosphonates
have been also examined in the literature. Maas and Hoge
reported first the possibility to carry out such cyclizations.2
They found that cyclic phosphonates could be obtained by
reaction of 2-isopropenylcyclopropylphosphonates and
phosphinates with bromine.2 Zhao and co-workers reported
that in the case of structurally less favored phosphonates,
bromine does not react, and only the reaction with iodine
was effective and led to the formation of five- and six-mem-
bered cyclic phosphonates.3 It was subsequently reported
that bromine could be also used for these cyclizations if
phosphonates monoesters were used.4 Cyclizations of allenic
phosphonic acids and phosphonates into 1,2-oxaphosphol-
3-enes have been also reported.5,6
2. Results
The substrates studied have been prepared as reported in
Scheme 1. Reaction of bromoalkenes 1a–e1b with dimethyl-
phosphite in the presence of sodium hydride in THF8 gave
rise to the formation of dimethylphosphates 2a–e in satisfac-
tory yields. The monohydrolysis to products 3a–e were then
carried out by reaction with 1 equiv of NaI in butan-2-one at
reflux. Methyl 3-phenylallylphosphonate 5 was obtained by
heating of cinnamyl bromide with trimethylphosphite,
O
O
OMe
OMe
P
P
NaI, EtCOMe
HP(O)(OMe)2
NaH, THF
Br
( ) n
( )n OH
( ) n OMe
1a-e n = 1-5
2a-e (32-98%)
3a-e (54-76%)
O
P
O
P
OMe
OH
OMe
OMe
P(OMe)3
NaI, EtCOMe
Ph
Ph
Br
Ph
Δ
4 (86%)
5 (100%)
Scheme 1.
Keywords: Electrophilic cyclization; Phosphocane; Phosphepane; Heterocycle; Halo reagent.
* Corresponding author. Tel.: +33 1 69 15 78 60; fax: +33 1 69 15 62 78; e-mail: grousseau@icmo.u-psud.fr
0040–4020/$ - see front matter Ó 2007 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tet.2007.07.032

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V. Andre et al. / Tetrahedron 63 (2007) 10059–10066
10060
Table 1. Reaction of phosphonate monoesters 3a–e and 5 with iodo- and bromo(bis-collidine) hexafluorophosphates
Entry
a
Substrate
Iodo phostone (yield, %)
Degradation
Bromo phostone (yield, %)
Degradation
O
OMe
P
3a
3b
3c
3d
3e
OH
O
O
e
OM
O
e
OM
O
O
P
P
OMe
P
b
c
d
e
7b (46)
Br 60:40a
6b (83)
()2
()3
()4
()5
OH
55:45a
I
O
P
O
P
OMe
O
OMe
O
O
P
OMe
OH
6c (76)
7c (67.5)
70:30a
Br
I
66:33a
O
OMe
O
O
P
P
OMe
OH
See text
6d (64.5)
62:38a
I
O
P
OMe
OH
Degradation
Degradation
O
O
OMe
OMe
O
P
P
P
8 (57)
65:35a
9 (44)
45:55a
OMe
OH
O
O
f
5
Ph
Ph
Ph
I
Br
a
Proportion of the diastereomers.
followed by monohydrolysis. The structure of products
2a–e, 3a–e, 4, and 5 were determined from their NMR, IR,
and mass spectra, and by comparison with the literature
data when possible (see Section 4).
We were then interested by application of these cyclizations
to the preparation of phospho sugars. Different methods
have been developed for their synthesis.9 However, the pos-
sibility to obtain such derivatives by electrophilic cyclization
of unsaturated phosphonates has not been yet examined. The
aim of our work was thus to apply this methodology to the
preparation of such derivatives according to the retro syn-
thetic pathway indicated in Scheme 2.
The reaction of compounds 3a–e and 5 with 1.3 equiv of
iodo- and bromo(bis-collidine) hexafluorophosphates were
carried out in dichloromethane at rt. Our results are reported
in Table 1.
O
O
O
OH
In the case of phosphonate monoesters 3b,c, we observed the
formation of the corresponding iodo- and bromo phostones
6b,c and 7b,c, in satisfactory yields. Their structures were de-
duced from their spectra data and confirmed by comparison
with the literature data for the known products. A mixture
of two diastereomers, due to the chiral phosphorus atom, is
observed in all cases. No product was obtained starting
from the allylphosphonate monoester 3a. These results are
not surprising, due to the probableverylow stability of the ex-
pected 1,2-oxaphosphetanes. Reaction of iodo(bis-collidine)
hexafluorophosphate with the phosphonate monoester 3d
led to the iodo phostone 6d in a satisfactory yield, while
reaction of bromo(bis-collidine) hexafluorophosphate led to
a complex mixture of products in which the endo and exo
cyclization products could be detected. However, they could
not be isolated in an enough pure state to be fully character-
ized. The formation of the eight-membered phostone was not
observed from phosphonate 3e. This failure, as in the case of
the carboxylic acids, is probably due to the fact that higher
activation energies are required for this ring size.1 In the
case of the phosphonate monoester 5, the stable endo cycliza-
tion products 8 and 9 were obtained. These endo cyclizations
were favored by the presence of the phenyl group.
R1O
R2O
O
P
X
OR4
R1O
R2O
P
OR4
H
OR4
OR3
OR3
OR3
Scheme 2.
Preparation of phosphonates 15 is outlined in Scheme 3.
Starting from L-tartaric acid, monoprotected diol 10 was
obtained using a reported procedure.10 Swern oxidation,
followed without purification of the aldehyde, by a Wittig re-
action, led to the unsaturated silyl ether 11.11 After cleavage
of the silyl ether, phosphonate 13 was then obtained as a mix-
ture of two diastereomers in a one-pot procedure by Swern
oxidation of alcohol 12 followed by addition of dimethyl-
phosphite. These diastereomers could not be separated by
liquid chromatography over silica gel. We were not able to
attribute the relative stereochemistry of these diastereomers
from their NMR spectra, even if in the literature the major
isomer was always reported to have the anti stereochemis-
try.12 Protection of its alcohol function as benzyl ether,13 al-
lowed a partial separation of the two diastereomers by liquid
chromatography over silica gel. In the conditions used for
this reaction, we observed a slight epimerization of the

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V. Andre et al. / Tetrahedron 63 (2007) 10059–10066
10061
HO
OSiMe2
t.Bu
OSiMe2 .Bu
t
HOOC
HO
COOH
OH
1. (ClCO)2, DMSO, NEt3
2. NaH, DMSO, MePPh3+ Br-
O
O
O
O
Me
Me
Me
Me
10 (41%)
11 (89%)
OBn
P
OH
O
O
OMe
OH
Ag2O, DMF
P
Bu4NF
THF
1. (ClCO)2, DMSO, NEt3
OMe
OMe
OMe
O
O
PhCH2Br
92%
O
O
O
O
2. HP(O)(OMe)2
93%
Me
Me
Me
Me
Me
Me
12 (83%)
13 (60:40)a
14 (78:22)a
OBn
O
O
OMe
O
BnO
P
-
Br+(coll)2 PF6
P
10% NaOH
OH
OMe
CH2Cl2
64%
O
O
H2O
52%
O
Me
Me
Br
O
Me
Me
15
16
Scheme 3. Preparation of oxaphosphepane 16. aProportion of the diastereomers.
minor diastereomer in favor of the major diastereomer
(78:22 ratio for the mixture of diastereomers 14 instead of
60:40 ratio for the mixture of diastereomers 13). The next
two steps were carried out on the major diastereomer and
on the mixture of the two diastereomers. Reaction with
10% NaOH led to the desired monoester phosphonate 15.
Subsequent reaction with bromo(bis-collidine) hexafluoro-
phosphate in dichloromethane led to 1,2-oxaphosphepane-
2-oxide 16. From the major phosphonate 15, a mixture of
two diastereomers (68:32) was obtained. The major diaste-
reomer was less polar. Their structures were established
without ambiguity from their 13C NMR spectra. The major
diastereomer shows in particular using J-mode experiments
a signal at 67.3 ppm attributed to the carbon in a of the
oxygen in the seven-membered cycle, which bears two
hydrogen atoms. The signal at 47.2 ppm, attributed to the
carbon in a of the bromine atom, bears only one hydrogen
atom. If we had the product of 6-exo cyclization, (product
16b in Scheme 5) the carbon in a of the oxygen atom should
bear one hydrogen atom, and that in a of the bromine atom
should bear two hydrogen atoms. The same observation was
made for the minor isomer, for which the carbon shifts were,
respectively, of 65.8 and 46.7 ppm. These conclusions were
confirmed by HSQC and HMBD experiments. Contrary to
our expectation, we did not observe the formation of the
six-membered phostones. The fact that in these cyclizations
only two diastereomers (corresponding to the chirality
induced by the phosphorus atom) were isolated, instead of
the four possible diastereomers can be explained by the
fact that the oxygen atom in a of the carbon–carbon double
bond directs the approach of the bromo reagent. However,
we were not able to determine certainly their stereochemis-
tries using NMR experiments (NOESY, COSY, etc.). At-
tempts to obtain crystal structure were also unsuccessful.
The presence of the dioxolane group seems to disfavor, for
steric reasons, the 6-exo mode cyclizations and favor the
7-endo mode ones. Reaction with the mixture of the two
diastereomers of compound 15 led to the formation of four
diastereomers. The very low stability of the iodo equivalent
of compound 16 did not allow its characterization. Some
1,2-oxaphosphepane-2-oxides are known.14 The good yields
observed in these cyclizations seem due to the presence of
the dioxolane group, which decreases the activation entropy
of these reactions,1,15 and allows a new preparation of this
family of compounds.
This particular behavior of unsaturated phosphonates 15 in
their reaction with bromo(bis-collidine) hexafluorophos-
phate led to examine the case of phosphonates in which
one supplementary carbon was introduced in the chain.
Such compounds should lead to the formation of still
unknown eight-membered heterocycles. The desired
u-ethylenic phosphonate was synthesized as outlined in
Scheme 4. As for the formation of a-hydroxyphosphonate
O
P
O
P
OBn
OH
Ag2O, DMF
PhCH2Br
OMe
OMe
OMe
OMe
1. (ClCO)2, DMSO, NEt3
OH
2. MeP(O)(OMe)2, BuLi
O
O
O
36%
O
O
59%
O
Me
Me
Me
Me
Me
Me
17 (80:20)a
18 (80:20)a
12
O
OMe
O
P
BnO
-
OH
OMe
Br+(coll)2 PF6
CH2Cl2
P
10% NaOH
H2O
BnO
O
O
O
45%
O
69%
Br
O
Me
Me
Me
Me
20 (69%)
19
Scheme 4. Preparation of phosphocane 20. aProportion of the diastereomers.

´
V. Andre et al. / Tetrahedron 63 (2007) 10059–10066
10062
13, the b-hydroxyphosphonate 17 has been obtained by
a one-pot procedure, by Swern oxidation of alcohol 12,
followed by reaction with [(dimethoxyphosphoryl)methyl]-
lithium. A mixture of the two diastereomers of compound
17 has been obtained in moderate yield. Here also, the stereo-
chemistry of the major diastereomer of 17 could not be
clearly established, even if in the literature, the anti stereo-
chemistry between the 3-hydroxyl function and the 4 oxygen
of the dioxolane group was reported to be favored.16 This not
very stable phosphonate 17 was protected as stable benzyl
ether 18. The two diastereomers of this ether were partially
separated by liquid chromatography over silica gel, so, the
next steps were carried out on the major diastereomer of
compound 18 and on the mixture of the two diastereomers,
in comparable yields. Reaction with 10% aqueous NaOH
with the major diastereomer of compound 18 led to the phos-
phonate monoester 19 and its reaction with bromo(bis-colli-
dine) hexafluorophosphate gave rise to the formation of the
phosphocane 20 (60:40 mixture of two diastereomers),
which structure was deduced from its NMR spectra. The
structural determinations were carried using in 13C NMR
J-mode experiments. In this case also, an endo mode cycliza-
tion was observed. The structure of compound 20 was estab-
lished without ambiguity from its 13C NMR spectra. The
major diastereomer shows in particular using J-mode exper-
iments a signal at 66.9 ppm attributed to the carbon in a of
the oxygen present in the eight-membered cycle. This carbon
bears two hydrogen atoms. In the same way, the signal at
51.4 ppm, attributed to the carbon in a of the bromine
atom, bears only one hydrogen atom. If we had the product
of 7-exo cyclization, (product 20b in Scheme 5) the carbon
in a of the oxygen atom should bear one hydrogen atom,
and that in a of the bromine atom should bear two hydrogen
atoms. The same observation was made for the minor isomer.
These conclusions were confirmed by HSQC and HMBD
experiments. As in the case of the formation of phostone
16, we observed only the formation of two diastereomers
instead of the four possible diastereomers. Here also the
dioxolane group directs the approach of the bromo reagent,
favors the endo mode cyclization and explains the yield
observed in this reaction. Attempts to determine the stereo-
chemistry of this phosphocane by NMR (NOESY, COSY,
etc.) were unsuccessful. When the cyclization was carried
out on the mixture of the two diastereomers of compound
19, an inseparable mixture of the expected four diastereo-
mers was obtained.
7-membered phostones formed by exo or endo mode cycliza-
tions have been observed for simple phosphonates. Contrary
to the results previously reported in the case of unsaturated
carboxylic acids,17 from b,g-unsaturated phosphonates,
4-membered phostones could not be obtained. In the case
of the unsaturated phosphonates 15 and 19, the formation
of endo cyclization products seems due to the conjunction
of different factors: the presence of the dioxolane group,
which favors the formation of the corresponding phostones
by endo mode cyclizations, the utilization of the bromo re-
agent, which is known to favor the endo cyclizations com-
pared to the iodo reagent,1 and the phosphonates, which in
certain cases, seems also to favor this kind of cyclizations,
by comparison with the reactivity of carboxylic acids.3 For
the first time, a phosphocane derivative has been synthe-
sized.
4. Experimental part
4.1. General
u-Ethylenic bromides 1b–e have been prepared as previ-
ously reported.1b Dimethyl allylphosphonate is commer-
cially available. All products were purified by flash liquid
chromatography using silica gel columns.
4.2. Preparation of dimethyl phosphonates 2b–e
These compounds were obtained by the Michaelis–Becker
reaction of bromides 1b–e with dimethyl phosphite. Under
argon, in a three neck, round-bottomed flask was added
successively NaH (60% in mineral oil, 2.54 g, 58 mmol,
1.3 equiv), dry THF (70 mL), and dimethylphosphite
(5.3 mL, 1.3 equiv). After stirring at 0 ꢀC (0.5 h), then at
reflux (1.5 h), bromides 1b–e (1 equiv) were introduced at
0 ꢀC. After stirring at rt (24 h), the reaction mixture was
quenched by addition of water (50 mL). The aqueous phase
was extracted with dichloromethane (3ꢁ50 mL). The organic
phases were dried (MgSO4), concentrated, and the residue
purified by chromatography over silica gel (MeOH–EtOAc).
Preparations of dimethyl but-3-enylphosphonate 2b (94%),4
dimethyl pent-4-enylphosphonate 2c (98%),3a and dimethyl
hex-5-enylphosphonate 2d (80%),18 have been reported.
Dimethyl hept-6-enylphosphonate 2e: yield 95%; 1H NMR
(360 MHz, CDCl3): d¼1.36–1.50 (m, 4H), 1.55–1.70 (m,
2H), 1.70–1.80 (m, 2H), 2.00–2.10 (m, 2H), 3.72 (d, J¼
10 Hz, 6H), 4.44–5.06 (m, 2H), 5.70–5.86 (m, 1H) ppm.
13C NMR (62.9 MHz, CDCl3): d¼21.5 (d, J¼5 Hz), 24.8
(d, J¼140 Hz), 27.6, 29.3 (d, J¼16 Hz), 32.7, 51.5 (d, J¼
6 Hz), 113.8, 137.9 ppm. HRMS (EI): [M+] calcd for
C9H19O3P: 206.1072. Found: 206.1073.
O
OMe
O
O
OMe
P
P
BnO
O
Br
BnO
Br
O
O
O
O
Me
Me
Me
20b
Me
4.3. (2E)-Dimethyl (3-phenylprop-2-enyl)-
phosphonate 419
16b
Scheme 5.
An oven-dried three neck, round-bottomed flask was
charged with a stoichiometric mixture of cinnamyl bromide
and trimethyl phosphite. After 2.5 h of heating at reflux, the
product was concentrated under vacuum, and purified by
liquid chromatography over silica gel (86%). 1H NMR
(250 MHz, CDCl3): d¼2.80 (dd, J¼25 and 7 Hz, 2H), 3.78
(d, J¼11 Hz, 6H), 6.08–6.25 (m, 1H), 6.55 (dd, J¼10 and
3. Conclusion
We have examined the scope of the reaction of u-unsatu-
rated phosphonate monoesters with iodo- and bromo(bis-
collidine) hexafluorophosphates. Formations of 5- to

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V. Andre et al. / Tetrahedron 63 (2007) 10059–10066
10063
5 Hz, 1H), 7.20–7.40 (m, 5H). 13C NMR (62.9 MHz,
CDCl3): d¼30.4 (d, J¼139 Hz), 53.1 (d, J¼7 Hz), 118.7
(d, J¼12 Hz), 126.6, 128.0, 128.9, 135.3 (d, J¼9 Hz),
139.0 ppm. 31P NMR (101.25 MHz, CDCl3): d¼22.5 ppm.
MS (ES) m/z: 265 (M++K+), 249 (M++Na+).
to continuous extraction with diethyl ether (12 h). The ethe-
real phase was dried (MgSO4), concentrated, and the residue
purified by liquid chromatography over silica gel (EtOAc).
The results are reported in Table 1. Phostones 6b,3b 6c,3a
7b,4 and 7c4 have been already described.
4.4. Preparation of methyl hydrogen
allylphosphonate 3a
4.9. 7-(Iodomethyl)-2-methoxy-1,2-oxaphosphepane-
2-oxide 6d
Under argon, in an oven-dried three neck round-bottomed
flask, was placed dimethylphosphonate 2a (50 mmol,
1 equiv), butan-2-one (50 mL), and sodium iodide
(51 mmol, 1.05 equiv). The mixture was heated at reflux
for 1 day. After cooling at 0 ꢀC, the solid formed was filtered,
washed with butan-2-one, and then solubilized in 1 N HCl
(50 mL). The solution was extracted with dichloromethane
(3ꢁ50 mL). The organic phases were dried (MgSO4), and
concentrated under vacuum, to give monoester 3a (90%),20
which was used without further purification for the cycliza-
tion. The monoesters 3b–e and 5 were prepared using the
same procedure. Methyl hydrogen but-3-enylphosphonate
3b (56%), and methyl hydrogen pent-4-enylphosphonate
3c (70%) have been already described.4
A mixture (62:38) of two diastereomers was isolated. Major
isomer (from the mixture) H NMR (200 MHz, CDCl3):
1
d¼1.58–2.35 (m, 8H), 3.35 (split AB system, DdAB
¼
29.8 Hz), 3.27 (part A, q, J¼10.6 and 7.6 Hz, 1H), 3.44
(part B, q, J¼4.7 and 10.7 Hz, 1H), 3.82 (d, J¼10.6 Hz,
3H), 4.04–4.30 (m, 1H) ppm. 13C NMR (62.9 MHz,
CDCl3): d¼8.6 (d, J¼5.6 Hz), 21.4 (d, J¼4 Hz), 26.0 (d,
J¼132.5 Hz), 27.1, 35.2, 52.1 (d, J¼7.3 Hz), 78.2 (d,
J¼4.6 Hz) ppm. HRMS (EI): [M+] calcd for C7H14IO3P:
304.0625. Found: 304.0626. Minor isomer (from the
1
mixture) H NMR (360 MHz, CDCl3): d¼1.56–2.20 (m,
8H), 3.32 (d, J¼7.5 Hz, 2H), 3.80 (d, J¼11.4 Hz, 3H),
4.26–4.42 (m, 1H) ppm. 13C NMR (62.9 MHz, CDCl3):
d¼9.5 (d, J¼9.5 Hz), 22.0 (d, J¼5 Hz), 26.6, 26.7
(d, J¼132 Hz), 25.7, 52.2 (d, J¼6.7 Hz), 75.8 (d,
J¼2H) ppm.
4.5. Methyl hydrogen hex-5-enylphosphonate 3d
Yield 60%; 1H NMR (250 MHz, CDCl3): d¼1.45–1.75 (m,
6H), 2.03 (q, J¼7 Hz, 2H), 3.65 (d, J¼11 Hz, 3H), 4.87–500
(m, 2H), 5.54–5.83 (m, 1H) ppm. 13C NMR (62.9 MHz,
CDCl3): d¼14.8, 27.9 (d, J¼140 Hz), 31.4, 33.2, 52.9
(d, J¼11 Hz), 114.4, 140.6 ppm. 31P NMR (101.2 MHz,
CDCl3): d¼38.6 ppm. HRMS (EI): [M+] calcd for
C7H15O3P: 178.0759. Found: 178.0758.
4.10. (4R*,5S*)-4-Iodo-2-methoxy-5-phenyl-1,2-
oxaphospholane 2-oxide 8
1H NMR (250 MHz, CDCl3) (mixture): d¼2.34–2.97 (m,
2H), 3.85 (d, J¼11 Hz, 3H (minor diastereomer)), 3.90 (d,
J¼11 Hz, 3H (major diastereomer)), 4.17–4.38 (m, 1H),
5.26 (d, J¼11 Hz, 1H (minor diastereomer)), 5.42 (dd, J¼3
and 11 Hz, 1H (major diastereomer)), 7.35–7.57 (m,
5H) ppm. 13C NMR (62.9 MHz, CDCl3) major diastereomer
(from the mixture): d¼19.5 (d, J¼8 Hz), 33.3 (d, J¼111 Hz),
54.5, 87.9, 127.0, 129.6, 129.6, 136.7 ppm. Minor diastereo-
mer (from the mixture): d¼19.6 (d, J¼8 Hz), 33.3 (d,
J¼111 Hz), 53.4, 87.8, 125.5, 126.1, 128.7, 135.6 ppm.
31P NMR (101.25 MHz, CDCl3): d¼42.8 ppm. IR (film):
4.6. Methyl hydrogen hept-6-enylphosphonate 3e
Yield 95%; 1H NMR (250 MHz, CDCl3): d¼1.30–1.50 (m,
14H), 1.50–1.90 (m, 4H), 1.90–2.05 (m, 2H), 3.72 (d,
J¼11 Hz, 3H), 4.95–5.05 (m, 2H), 5.70–5.86 (m, 1H),
11.83 (br s, 1H) ppm. HRMS (EI): [M+] calcd for
C8H17O3P: 192.0915. Found: 192.0916.
n 1192, 1046 (nP]O) cmꢂ1
.
4.7. (2E)-Methyl hydrogen (3-phenylprop-2-enyl)-
phosphonate 5
4.11. (4R*,5S*)-4-Bromo-2-methoxy-5-phenyl-1,2-
oxaphospholane 2-oxide 9
Yield 90%; 1H NMR (250 MHz, CDCl3): d¼2.73 (dd, J¼23
and 6 Hz, 2H), 3.66 (d, J¼11 Hz, 3H), 6.13 (m, 1H), 6.52 (dd,
J¼16 and 5 Hz, 1H), 7.14–7.50 (m, 5H), 10.83 (br s,
1H) ppm. 13C NMR (62.9 MHz, CDCl3): d¼31.2 (d,
J¼142 Hz), 52.7 (d, J¼5 Hz), 118.9 (d, J¼12 Hz), 126.8,
128.2, 129.1, 135.5 (d, J¼15 Hz), 137.4 ppm. 31P NMR
(101.25 MHz, CDCl3) d¼23.24 ppm. IR (film): n 1638
(nC]C), 1234.5 (nP]O) cmꢂ1. HRMS (EI): calcd for
C10H13O3P: 212.0602. Found: 212.0603.
1H NMR (200 MHz, CDCl3) (mixture): d¼2.31–2.98 (m,
2H), 3.89 (d, J¼12 Hz, 3H (minor diastereomer)), 3.95 (d,
J¼11 Hz, 3H (major diastereomer)), 4.15–4.40 (m, 1H),
5.20 (d, J¼8 Hz, 1H), 5.32 (dd, J¼2 and 8 Hz, 1H), 7.30–
7.60 (m, 5H) ppm. 13C NMR (50.3 MHz, CDCl3) major
diastereomer (from the mixture): d¼31.6 (d, J¼113 Hz),
46.2 (d, J¼12 Hz), 53.5 (d, J¼6 Hz), 86.2 (d, J¼4 Hz),
126.7, 128.7, 129.5, 135.8 ppm. Minor diastereomer
(from the mixture): d¼31.3 (d, J¼115 Hz), 46.4 (d,
J¼11 Hz), 53.6 (d, J¼6 Hz), 85.9 (d, J¼5 Hz), 126.7,
128.7, 129.5, 135.7 ppm. IR (film): n 1639, 1250, 1042
4.8. General procedure for the halo cyclizations
(nP]O) cmꢂ1
.
To a dichloromethane solution (50 mL) of halo(bis-colli-
dine) hexafluorophosphate21 (3.6 mmol, 1.3 equiv) was
added in the dark, in 2 h, a dichloromethane solution
(30 mL) of monoester phosphonate (3 mmol). After 1 h at
rt, the solvent was removed under vacuum and 1 N HCl
(50 mL) was added. This aqueous phase was then subjected
4.12. [(4S,5S)-5-({[tert-Butyldimethylsilyl]oxy}methyl)-
2,2-dimethyl-1,3-dioxolan-4-yl]methanol 10
This compound has been obtained by a reported procedure,
starting from L-tartaric acid.10

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V. Andre et al. / Tetrahedron 63 (2007) 10059–10066
10064
4.13. {[(4S,5S)-2,2-Dimethyl-5-vinyl-1,3-dioxolan-4-yl]-
methoxy}tert-butyldimethylsilane 11
J¼6 Hz), 67.9 (d, J¼162 Hz), 78.8 (d, J¼8 Hz), 80.1 (d,
J¼5 Hz), 109.4, 117.4, 135.8 ppm. HRMS (ESI): [M++Na]
calcd for C10H19NaO6P: 289.0817. Found: 289.0815.
A dichloromethane solution (175 mL) of dimethylsulfoxide
(28.1 mL, 0.4 mol, 2.8 equiv) was added slowly at ꢂ50 ꢀC
to a dichloromethane solution (375 mL) of oxalyl chloride
(18.7 mL, 0.213 mol, 1.5 equiv). After the end of the addi-
tion the dichloromethane solution was stirred for 15 min,
and then a dichloromethane solution (175 mL) of alcohol
10 (0.142 mol, 39.2 g, 1 equiv) was added. After 20 min at
ꢂ50 ꢀC, triethylamine was added (198 mL, 1.42 mol,
10 equiv), and the solution stirred 15 min at ꢂ50 ꢀC. Then,
the flask was warmed to rt, and the dichloromethane solution
was washed twice with a saturated solution of NaCl, dried
(Mg2SO4), and concentrated. The crude aldehyde was used
without purification for the next step.
4.16. Dimethyl (benzyloxy)((4R,5S)-2,2-dimethyl-5-
vinyl-1,3-dioxolan-4-yl)methylphosphonate 14
To a DMF solution (20 mL) of hydroxyphosphonate 13
(1.825 g, 6.86 mmol) was added benzyl bromide (0.896 mL,
7.6 mmol, 1.1 equiv) and Ag2O (1.756 g). After 48 h at rt,
the mixture was filtered over Celite, and the solution was pu-
rified by liquid chromatography over silica gel (diethyl ether)
to give 2.23 g of benzyl ether 14 as a mixture (92%) of two
diastereomers (78:22). A partial separation of the two diaste-
reomers was possible. Major diastereomer: 1H NMR
(250 MHz, CDCl3): d¼1.42 (s, 3H), 1.46 (s, 3H), 3.75 (d,
J¼10 Hz, 3H), 3.78 (d, J¼10 Hz, 3H), 4.00 (dd, J¼3 and
11 Hz, 1H), 4.10–4.15 (m, 1H), 4.61 (t, J¼6 Hz, 1H), 4.80
(AB system, Dd¼0.08, J¼11 Hz, 2H), 5.19–5.44 (m, 2H),
5.78–5.98 (m, 1H), 7.30–7.47 (m, 5H) ppm. 13C NMR
(62.9 MHz, CDCl3): d¼26.5, 27.0, 52.6 (d, J¼7 Hz), 53.5
(d, J¼6 Hz), 71.2 (d, J¼165 Hz), 74.1, 77.7 (d, J¼13 Hz),
79.4, 109.5, 119.3, 128.2, 128.4, 128.8, 134.6, 136.6 ppm.
31P NMR (101.12 MHz, CDCl3): d¼21.96 ppm. HRMS
(ESI): [M++Na] calcd for C17H25NaO6P: 379.1286. Found:
379.1288. Minor diastereomer: 1H NMR (250 MHz,
CDCl3): d¼1.44 (s, 3H), 3.84 (d, J¼11 Hz, 3H), 3.86
(d, J¼11 Hz, 3H), 3.70 (dd, J¼2 and 8 Hz, 1H), 3.93–4.05
(m, 1H), 4.32 (t, J¼8 Hz, 1H), 4.78 (AB system, Dd¼0.29,
J¼11 Hz, 2H), 4.80–5.14 (m, 2H), 5.55–5.76 (m, 1H),
7.28–7.45 (m, 5H) ppm. 31P NMR (101.2 MHz, CDCl3):
d¼24.0 ppm. HRMS (ESI): [M++Na] calcd for
C17H25NaO6P: 379.1286. Found: 379.1291.
To a suspension of NaH (60% in mineral oil, 11.4 g) in THF
(190 mL) cooled at 0 ꢀC was added dry dimethylsulfoxide
(49.6 mL, 2 equiv). After 30 min at rt, this solution was
transferred into a THF solution (870 mL) of methyltriphen-
ylphosphonium bromide (101.5 g, 2 equiv). After stirring
2 h at rt, a THF solution (190 mL) of the aldehyde was added
at 0 ꢀC, and the resulting mixture was stirred one night at rt.
After addition of ether (1 L), the solid was filtered, and the
solution was concentrated under vacuum. The residue was
purified by liquid chromatography over silica gel (pentane
to pentane–ether (1:1)), to give the desired olefin 11
(16.3 g, 84%).22
4.14. [(4S,5S)-2,2-Dimethyl-5-vinyl-1,3-dioxolan-4-yl]-
methanol 12
This compound was prepared as previously reported.22
4.17. Methyl hydrogen (benzyloxy)((4R,5S)-2,2-di-
methyl-5-vinyl-1,3-dioxolan-4-yl)methylphosphonate 15
4.15. Dimethyl hydroxy((4R,5S)-2,2-dimethyl-5-vinyl-
1,3-dioxolan-4-yl)methylphosphonate 13
A solution of the major diastereomer of dimethylphospho-
nate 14 (0.178 g, 0.5 mmol) in 1 N NaOH (0.86 mL) was
heated at reflux (7 h). After cooling, 12 N HCl was added
to adjust at pH 5, followed by saturated NaCl solution
(2 mL). The aqueous phase was extracted with chloroform
(5ꢁ3 mL). The organic phases were dried (Na2SO4) and
concentrated under vacuum. The residue was then purified
by liquid chromatography over silica gel (EtOAc–MeOH):
1H NMR (250 MHz, CDCl3): d¼1.38 (s, 3H), 1.42 (s,
3H), 3.60 (br d, J¼8 Hz, 3H), 3.93 (br d, J¼11 Hz, 1H),
4.05–4.25 (m, 1H), 4.50–5.00 (m, 3H), 5.00–5.50 (m, 2H),
5.80–6.15 (m, 1H), 7.20–7.47 (m, 5H), 7.55 (br s,
1H) ppm. 13C NMR (62.9 MHz, CDCl3): d¼26.9, 27.0,
53.2, 74.2, 75.4, 77.7, 80.9, 109.1, 116.8, 127.8, 128.3,
136.5, 137.8 ppm. 31P NMR (101.2 MHz, CDCl3): d¼
16.7 ppm. IR (CDCl3 solution): n 3412, 3019, 1645, 1265,
1216, 1048, 929 cmꢂ1. HRMS (ESI): [M++Na] calcd for
C16H23NaO6P: 365.1130. Found: 365.1124. The same reac-
tion was carried out with the mixture of diastereomers of
phosphonate 14. Minor diastereomer (from the mixture):
1H NMR (250 MHz, CDCl3): d¼1.36 (s, 6H), 3.40–3.75
(m, 2H), 3.61 (dt, J¼1 and 10 Hz, 3H), 4.67 (t, J¼11 Hz,
1H), 4.72–5.16 (m, 4H), 5.45–5.65 (m, 1H), 7.17–7.23 (m,
5H), 7.46–7.82 (m, 1H) ppm. 31P NMR (101.2 MHz,
CDCl3): d¼20.9 ppm. HRMS (ESI): [M++Na] calcd for
C16H23NaO6P: 365.1130. Found: 365.1130.
A dichloromethane solution (45 mL) of dimethylsulfoxide
(2.78 mL, 39.16 mmol, 3.0 equiv) was added slowly at
ꢂ50 ꢀC to a dichloromethane solution (40 ml) of oxalyl chlo-
ride (1.68 mL, 19.6 mmol, 1.5 equiv). The dichloromethane
solution was stirred for 15 min, and then a dichloromethane
solution (90 mL) of alcohol 12 (2.06 g, 13 mmol) was added
slowly. After 30 min at ꢂ50 ꢀC, triethylamine (9.2 mL,
65.25 mmol, 5 equiv) was added. After cooling at rt, di-
methylphosphite (2.4 mL, 26.10 mmol, 2 equiv) was added
and theresulting mixturewas stirredovernight. Afteraddition
of water (200 mL), the organic phase was separated, and the
aqueous phase was extracted with chloroform (4ꢁ200 mL).
The organic phases were dried and concentrated under vac-
uum. The residue was purified by liquid chromatography
over silica gel (EtOAc) to give the hydroxyphosphonate 13
as a mixture of two diastereomers (60:40) 2.55 g (73%). 1H
NMR (250 MHz, CDCl3) (mixture): d¼1.44 (s, 2.4H), 1.48
(s, 3.6H), 3.83 (d, J¼10 Hz, 0.6H), 3.85 (d, J¼10 Hz,
0.4H), 4.00–4.19 (m, 2H), 4.47 (t, J¼8 Hz, 0.4H), 4.64 (t,
J¼7 Hz, 0.6H), 5.20–5.53 (m, 2H), 5.73–6.13 (m, 1H) ppm.
13C NMR (62.9 MHz, CDCl3) minor diastereomer (from
the mixture): d¼26.5, 26.9, 53.0 (d, J¼6 Hz), 53.6 (d, J¼
6 Hz), 64.5 (d, J¼163 Hz), 77.9 (d, J¼14 Hz), 78.7 (d, J¼
6 Hz), 109.8, 119.8, 134.2 ppm. Major diastereomer (from
the mixture): d¼26.7, 26.8, 53.1 (d, J¼6 Hz), 53.3 (d,

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V. Andre et al. / Tetrahedron 63 (2007) 10059–10066
10065
4.18. (3aS,8aS)-4-(Benzyloxy)-8-bromo-5-methoxy-2,2-
dimethylhexahydro[1,3]dioxolo[4,5-d][1,2]oxaphos-
phepine 5-oxide 16
136.4 ppm. Minor diastereomer (from the mixture):
d¼26.9, 30.1 (d, J¼140 Hz), 51.9–52.8 (2d), 64.6 (d, J¼
4 Hz), 78.3, 83.2 (d, J¼15 Hz), 109.3, 119.3, 135.2 ppm.
31P NMR (101.2 MHz, CDCl3): d¼32.7 (major diastereo-
mer), 33.3 (minor diastereomer) ppm. IR (CDCl3, mixture):
n 3436, 3020, 1476, 1216, 1044, 929 cmꢂ1. HRMS (ESI):
[M++Na] calcd for C11H21NaO6P: 303.0973. Found:
303.0968.
To a dichloromethane solution (4 mL) of the major diaste-
reomer of compound 15 (126 mg, 0.37 mmol) was added
in 1 h a dichloromethane solution (3 mL) of bromo(bis-
collidine) hexafluorophosphate (225 mg, 6.48 mmol). After
12 h at rt, the reaction mixture was concentrated under vac-
uum, and the residue was purified by liquid chromatography
over silica gel (EtOAc–hexanes 60:40). A mixture of two
diastereomers (68:32) was obtained. A fraction containing
only the less polar diastereomer could be isolated. Major
diastereomer (less polar) 1H NMR (400 MHz, CDCl3):
d¼1.39 (s, 3H), 1.42 (s, 3H), 3.77 (d, J¼11 Hz, 3H), 4.06
(dt, J¼4 and 10 Hz, 1H), 4.11–4.42 (m, 5H), 4.71 (s, 2H),
7.21–7.34 (m, 5H) ppm. 13C NMR (62.9 MHz, CDCl3):
d¼26.5, 26.9, 47.2, 53.2 (d, J¼7 Hz), 67.3 (d, J¼7 Hz),
73.0 (d, J¼149 Hz), 76.2 (d, J¼5 Hz), 78.2 (d, J¼19 Hz),
78.7, 109.6, 128.2, 128.3, 128.5, 136.7 ppm. 31P NMR
(101.2 MHz, CDCl3): d¼23.7 ppm. IR (CDCl3 solution): n
3019, 1455, 1256, 1215, 1021 cmꢂ1. HRMS (ESI):
[M++Na] calcd for C16H22BrNaO6P: 443.0235. Found:
443.02360. [a]2D3 +19.5 (c 1, CHCl3). Minor diastereomer
(more polar): 1H NMR (250 MHz, CDCl3): d¼1.37 (s,
3H), 1.40 (s, 3H), 3.67 (d, J¼14 Hz, 3H), 3.72–4.50 (m,
6H), 4.79 (AB system, Dd¼0.261 ppm, J¼12 Hz, 2H),
7.19–7.30 (m, 5H). 13C NMR (62.9 MHz, CDCl3):
d¼26.3, 27.1, 46.9, 52.6 (d, J¼7 Hz), 65.8 (d, J¼4 Hz),
71.3 (d, J¼150 Hz), 74.8, 78.4, 78.7 (d, J¼17 Hz), 109.4,
128.1, 128.3, 128.4, 136.9. 31P NMR (101.2 MHz,
CDCl3): d¼23.7. IR (CDCl3 solution): n 1643, 1455,
1261, 1042, 650 cmꢂ1. HRMS (ESI): [M++Na] calcd for
C16H22BrNaO6P: 443.0235. Found: 443.0230. When the
bromo phostonization was carried out on the mixture of
the two diastereomers of compound 16, an inseparable
mixture of four diastereomers was obtained.
4.20. Dimethyl 2-(benzyloxy)-2-((4R,5S)-2,2-dimethyl-
5-vinyl-1,3-dioxolan-4-yl)ethylphosphonate 18
This compound has been prepared following the method
reported for the preparation of compound 14. A partial
separation of the two diastereomers (80:20) could be carried
out. Major diastereomer: 1H NMR (250 MHz, CDCl3):
d¼1.43 (s, 6H), 2.00–2.30 (m, 2H), 3.60–3.80 (m, 3H),
3.95–4.18 (m, 1H), 4.34 (t, J¼2 Hz, 1H), 4.72 (s, 2H),
5.07–5.48 (m, 2H), 5.70–5.98 (m, 1H), 7.20–7.45 (m,
5H) ppm. 13C NMR (62.9 MHz, CDCl3): d¼26.8, 27.4 (d,
J¼143 Hz), 52.4 (d, J¼5 Hz), 74.0 (d, J¼4 Hz), 78.8,
82.1 (d, J¼17 Hz), 109.2, 118.6, 127.6, 127.9, 128.2,
135.9, 137.5 ppm. 31P NMR (101.2 MHz, CDCl3): d¼
31.6 ppm. IR (CDCl3 solution): n 3401, 3019, 1243,
1216, 1041 cmꢂ1. HRMS (ESI): [M++Na] calcd for
C18H27NaO6P: 393.1443. Found: 393.1444. Minor dia-
stereomer (from the mixture): 1H NMR (250 MHz,
CDCl3): d¼1.37 (s, 6H), 1.78–2.32 (m, 2H), 3.50–3.80
(m, 7H), 3.80–4.08 (m, 1H), 4.22–4.85 (m, 3H), 4.85–5.35
(m, 2H), 5.64–5.92 (m, 1H), 7.10–7.20 (m, 5H) ppm. 31P
NMR (101.2 MHz, CDCl3): d¼28.0 ppm.
4.21. Methyl hydrogen 2-(benzyloxy)-2-((4R,5S)-2,2-
dimethyl-5-vinyl-1,3-dioxolan-4-yl)ethylphosphonate 19
This compound has been prepared following the method
reported for the preparation of compound 15 (34%). Major
diastereomer: 1H NMR (250 MHz, CDCl3): d¼1.32 (s,
3H), 1.34 (s, 3H), 1.84–2.20 (m, 2H), 3.55 (d, J¼11 Hz,
3H), 3.73–3.87 (m, 1H), 3.87–4.15 (m, 1H), 4.32 (t,
J¼7 Hz, 1H), 4.63 (AB system, Dd¼0.067, J¼11 Hz, 2H),
5.02–5.40 (m, 2H), 5.60–5.89 (m, 1H), 7.05–7.35 (m, 5H),
8.10–8.70 (m, 1H) ppm. 13C NMR (62.9 MHz, CDCl3):
d¼26.9, 28.4 (d, J¼143 Hz), 51.6 (d, J¼5.6 Hz), 73.2,
74.2, 78.7, 82.6 (d, J¼12 Hz), 109.2, 118.8, 127.6, 128.0,
128.2, 136.2, 138.0 ppm. 31P NMR (101.2 MHz, CDCl3):
d¼32.0 ppm. IR (CDCl3 solution): n 3401, 2981, 1647,
1116.6, 1215, 1054, 987 cmꢂ1. HRMS (ESI): [M++Na]
calcd for C17H25NaO6P: 379.1286. Found: 379.1290.
4.19. Dimethyl 2-hydroxy-2-((4S,5S)-2,2-dimethyl-5-
vinyl-1,3-dioxolan-4-yl)ethylphosphonate 17
The Swern oxidation of alcohol 12 was carried out as
reported for the preparation of compound 13. The dichloro-
methane solution of the crude aldehyde (5 mmol) was cooled
at ꢂ78 ꢀC. In a second flask cooled at ꢂ78 ꢀC, containing
a THF solution (16 mL) of dimethyl methylphosphonate
(10 mmol, 2 equiv), was added 1.6 M nBuLi in hexane
(10 mmol). After 45 min at this temperature the contents
of this flask was cannulated into the flask containing the
crude aldehyde. After 15 min, the reaction mixture was
warmed to rt. After addition of aqueous ammonium chloride,
the organic phase was separated and the aqueous phase
extracted with chloroform (3ꢁ50 mL). After drying of the
organic phases (Na2SO4), concentration under vacuum, the
residue was purified by liquid chromatography over silica
gel (EtOAc). The two diastereomers (80:20) of compound
4.22. (3aS,9aS)-9-(Benzyloxy)-4-bromo-2,2-dimethyl-7-
methoxy-hexahydro-3aH-[1,3]dioxolo[4,5-e][1,2]oxa-
phosphocine 7-oxide 20
The reaction was carried out following the method reported
for the preparation of phostone 16. Starting from the major
diastereomer of phosphonate 19, a mixture of two diastereo-
mers of 20 was obtained (60:40), from which the less polar
diastereomer could be obtained in pure form. Less polar
diastereomer: 1H NMR (250 MHz, CDCl3): d¼1.38 (s, 3H),
1.44 (s, 3H), 1.95–2.45 (m, 2H), 3.67 (d, J¼9 Hz, 3H),
4.00–4.20 (m, 3H), 4.22–4.40 (m, 2H), 4.49 (dd, J¼2.5
and 7 Hz, 1H), 4.67 (AB system, Dd¼0.3, J¼12 Hz, 2H),
1
17 could not be separated. H NMR (200 MHz, CDCl3)
(mixture): d¼1.42 (s, 3H), 1.44 (s, 3H), 1.80–2.38 (m,
2H), 3.65–3.83 (m, 7H), 3.96–4.20 (m, 1H), 4.40 (t,
J¼7 Hz, 1H), 5.12–5.43 (m, 2H), 5.73–6.02 (m, 1H) ppm.
13C NMR (62.9 MHz, CDCl3) major diastereomer (from
the mixture): d¼26.9, 29.2 (d, J¼140 Hz), 51.9–52.8 (2d),
67.6 (d, J¼5 Hz), 79.9, 83.3 (d, J¼16 Hz), 109.3, 117.6,

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V. Andre et al. / Tetrahedron 63 (2007) 10059–10066
10066
7.22–7.34 (m, 5H) ppm. 13C NMR (62.9 MHz, CDCl3):
d¼26.1 (d, J¼130 Hz), 26.6, 26.8, 51.4 (d, J¼2 Hz), 52.0
(d, J¼7 Hz), 66.9 (d, J¼7 Hz), 71.1 (d, J¼4 Hz), 74.2,
79.3, 80.4, 109.4, 127.7, 127.9, 128.4, 137.8 ppm. 31P
NMR (101.2 MHz, CDCl3): d¼25.8 ppm. IR (CDCl3 solu-
tion): n 1641, 1471, 1261, 1212, 1042, 650 cmꢂ1. HRMS
m/z calcd for C17H24BrNaO6P: 457.0392. Found: 457.0392.
[a]2D3 +4 (c 0.35, CHCl3). More polar diastereomer (from
the mixture): 1H NMR (250 MHz, CDCl3): d¼1.35 (s, 3H),
1.37 (s, 3H), 1.99–2.42 (m, 2H), 3.66 (d, J¼11 Hz, 3H),
4.00–4.20 (m, 6H), 4.51–4.74 (m, 2H), 7.19–7.35 (m,
5H) ppm. 13C NMR (62.9 MHz, CDCl3): d¼26.6, 26.8,
27.9 (d, J¼136 Hz), 50.8 (d, J¼3 Hz), 51.7 (d, J¼7 Hz),
66.5 (d, J¼4 Hz), 72.6 (d, J¼4 Hz), 72.9, 78.9, 81.8, 108.3,
127.6, 127.9, 128.4, 137.5 ppm. 31P NMR (101.2 MHz,
CDCl3): d¼27.9 ppm. IR (CDCl3 solution): n 2992, 1639,
1462, 1255, 1050 cmꢂ1. HRMS (ESI): [M++Na] calcd for
C17H24BrNaO6P: 457.0392. Found: 457.0391. When the
reaction was carried out with a mixture (2:1) of the two
diastereomers of compound 19, an inseparable mixture
(33:33:17:17) of four diastereomers of compound 20 was
obtained.
7. Lahrache, H.; Robin, S.; Rousseau, G. Tetrahedron Lett. 2005,
46, 1635–1637.
8. Bigge, C. F.; Drummond, J. T.; Johnson, G.; Malone, T.; Probert,
A. W., Jr.; Marcoux, F. W.; Coughenour, L. L.; Brahce, L. J.
J. Med. Chem. 1989, 32, 1580–1590.
9. Stoianova, D. S.; Whitehead, A.; Hanson, P. R. J. Org. Chem.
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3337–3342.
11. Chen, J.; Marx, J. N. Tetrahedron Lett. 1997, 38, 1889–1892.
12. See for example: (a) Wroblewski, A. E.; Balcerzak, K. B.
Tetrahedron 1998, 54, 6833–6840; (b) Chen, X.; Wiemer,
A. J.; Hohl, R. J.; Wiemer, D. F. J. Org. Chem. 2002, 67,
9331–9339.
13. Grembecka, J.; Mucha, A.; Cierpicki, T.; Kafarski, P. J. Med.
Chem. 2003, 46, 2641–2655.
14. (a) Bergesen, K. Acta Chem. Scand. 1968, 22, 1366–1367; (b)
Knochel, P.; Normant, J. F. J. Organomet. Chem. 1986, 309,
1–23; (c) Thiem, J.; Guenther, M. Phosphorus Sulfur Relat.
Elem. 1984, 20, 67–79; (d) Timmer, M. S. M.; Ovaa, H.;
Filippov, D. V.; Van der Marel, G. A.; Van Boom, J. H.
Tetrahedron Lett. 2001, 42, 8231–8233; (e) Mironov, V. F.;
Zagidullina, E. R.; Ivkova, G. A.; Dobrynin, A. B.;
Gubaidullin, A. T.; Latypov, S. K.; Musin, R. Z.; Litvinov, I.
A.; Balandina, A. A.; Konovalova, I. R. http://www.arkat-usa.
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References and notes
ꢀ
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1. (a) Rousseau, G.; Homsi, F. Chem. Soc. Rev. 1997, 26, 453–461;
(b) Roux, M.-C.; Paugam, R.; Rousseau, G. J. Org. Chem. 2001,
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