Spontaneous Nef reaction of 3-aryl-2-(diethoxyphosphoryl)-4-nitroalkanoic acids

Article abstract of DOI:10.1016/j.tet.2006.07.041

Spontaneous Nef reaction of primary and secondary 3-aryl-2-(diethoxyphosphoryl)-4-nitroalkanoic acids has been observed for?the first time. The reaction provides a general and effective, highly diastereoselective synthesis of 3-(diethoxyphosphoryl)-1-hydr

Full text of DOI:10.1016/j.tet.2006.07.041

Tetrahedron 62 (2006) 9135–9145
Spontaneous Nef reaction of 3-aryl-2-(diethoxyphosphoryl)-
4-nitroalkanoic acids
a
b
b
Henryk Krawczyk,a, qukasz Albrecht, Jakub Wojciechowski and Wojciech M. Wolf
*
a
_
Technical University (Politechnika), Institute of Organic Chemistry, Zeromskiego 116, 90-924 Łoꢀdꢀz, Poland
b
_
Technical University (Politechnika), Institute of General and Ecological Chemistry, Zeromskiego 116, 90-924 Łoꢀdꢀz, Poland
Received 28 April 2006; revised 25 June 2006; accepted 13 July 2006
Available online 8 August 2006
Abstract—Spontaneous Nef reaction of primary and secondary 3-aryl-2-(diethoxyphosphoryl)-4-nitroalkanoic acids has been observed
for the first time. The reaction provides a general and effective, highly diastereoselective synthesis of 3-(diethoxyphosphoryl)-1-hydroxy-
succinimides and 2-(diethoxyphosphoryl)-4-oxoalkanoic acids.
Ó 2006 Elsevier Ltd. All rights reserved.
1. Introduction
recently discovered that these lactones can also be success-
fully used as starting materials for the preparation of ethyl
cyclopropanecarboxylates.16
Acid promoted hydrolysis of primary and secondary nitroal-
kanes to the corresponding carbonyl compounds, commonly
known as the Nef reaction, represents a synthetically impor-
tant transformation.1–3 The ability to transform a nitroalkane
to an aldehyde or ketone makes the nitro group a masked car-
bonyl group. Considerable effort has been devoted to opti-
mize conditions of this reaction. Within this area, we have
recently demonstrated that the carboxylic acid functionality
participates as an intramolecular catalyst in the Nef reaction
of primary and secondary 2-(diethoxyphosphoryl)-4-nitro-
alkanoic acids.4 We have found that this reaction proceeds
in water in the absence of any additives. Under these condi-
tions 2-(diethoxyphosphoryl)-4-nitrobutanoic acid underwent
conversion into 3-(diethoxyphosphoryl)-1-hydroxysuccin-
imide, while 2-(diethoxyphosphoryl)-4-nitropentanoic and
hexanoic acids afforded the corresponding 2-(diethoxyphos-
phoryl)-4-oxoalkanoic acids.
The Nef reaction based on the intramolecular catalysis
would significantly benefit from availability of substituted
2-(diethoxyphosphoryl)-4-nitroalkanoic acids. Recently, we
have described an efficient route to (E)-3-aryl-2-(diethoxy-
phosphoryl)acrylic acids 1.17 In this paper we report that
a variety of 3-(diethoxyphosphoryl)-1-hydroxysuccinimides
8a–e and 2-(diethoxyphosphoryl)-4-oxopentanoic acids
9a–e can be prepared by addition of nitromethane or nitro-
ethane to the acids 1a–e, and subsequent spontaneous Nef
reaction of the resulting 2-(diethoxyphosphoryl)-4-nitro-
butanoic acids 5a–e and 2-(diethoxyphosphoryl)-4-nitro-
pentanoic acids 6a–e, respectively.
2. Results and discussion
Intramolecular catalysis of the Nef reaction represents a
conceptually new approach to the preparation of 1-hydroxy-
succinimides,5 and provides an attractive entry to 2-(diethoxy-
phosphoryl)-4-oxoalkanoic acids.6–10 Thelattertransformation
would be very valuable in the synthesis of a-diethoxy-
phosphoryl-g-butyrolactones. There has been an intense
activity in the application of a-diethoxyphosphoryl-g-
lactones for the preparation of their a-alkylidene derivatives
by Horner–Wadsworth–Emmons olefination.11–15 We have
Our initial attempts to obtain the nitroalkanoic acids 5a–e
and 6a–e by a self-catalytic Michael addition of nitrometh-
ane and nitroethane to the dicyclohexylammonium salts of
acids 1a–e under previously reported conditions were unsuc-
cessful.4,17 In all cases the unreacted starting materials were
recovered. The problem was eventually solved by modifying
the Michael acceptor. tert-Butyl acrylates 2a–e were gener-
ated by treatment of the acids 1a–e with tert-butyl alcohol
in the presence of magnesium sulfate and sulfuric acid
(Scheme 1 and Table 1).18 It was found that the use of the
nitroalkane as both the reagent and the solvent with potas-
sium tert-butoxide (50 mol %) as a catalyst gave the best
results in terms of yield and purity of the products. The
addition proceeded effectively at room temperature. The
Keywords: Intramolecular catalysis; Nef reaction; Michael reaction;
4-Oxoalkanoic acids; N-Hydroxysuccinimides.
* Corresponding author. Fax: +48 42 6365530; e-mail: henkrawc@p.lodz.pl
0040–4020/$ - see front matter Ó 2006 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tet.2006.07.041

9136
H. Krawczyk et al. / Tetrahedron 62 (2006) 9135–9145
O
O
O
O
(EtO)2P
COOH
NO2
R
(EtO)2P
COOt-Bu
NO2
(EtO)2P
COOH
Ar
(EtO)2P
COOt-Bu
a
b
c
Ar
Ar
Ar
R
(2R*,3R*)-3a-e R = H
3d de = 48%
(2R*,3R*)-5a-e R = H
(2R*,3R*,4R*)-6a-e R = CH3
1a-e
2a-e
3e de = 48%
(2R*,3R*,4R*)-4a-e R = CH3
Scheme 1. Reagents and conditions: (a) MgSO4 (5 equiv), H2SO4 (1 equiv), t-BuOH (4 equiv), CH2Cl2, rt; (b) MeNO2 or EtNO2, t-BuOK (0.5 equiv), rt; and (c)
CF3COOH–CH2Cl2 (1:1), rt, 24 h.
Table 1. tert-Butyl acrylates 2, nitroalkanoates 3 and 4, and nitroalkanoic acids 5 and 6 prepared
Ar
2
3 (R¼H)
4 (R¼CH3)
5
6
Yield [%]
Reaction
time [days]
Yield [%]
Reaction
time [days]
Yield [%]
Reaction
time [days]
(R¼H)
(R¼CH3)
Yield [%]
Yield [%]
a
b
c
4-NO2–C6H4–
4-Br–C6H4–
4-CH3–C6H4–
4-CH3O–C6H4–
O
82
85
88
82
2
2
4
4
90
67
80
56
1
1
8
24
70
66
49
58
1
1
4
5
90
80
89
77
85
89
84
92
d
e
91
3
73
11
51
5
94
93
O
O
yields of the products obtained from nitromethane were sim-
ilar to those derived from nitroethane. However, the addition
of nitromethane to the acrylates 2a–e was much slower and
was highly dependant on the particular electrophile used.
CH3 P(OEt)2
O2N
COOt-Bu
The products 3a–e and 4a–e were formed as mixtures of
diastereoisomers. Notably, the crystalline nitroalkanoates
3a–c and 4a–e were isolated as single diastereoisomers. In
each case, the crystalline adduct was the major diastereoiso-
mer present in the reaction mixture. This result indicates that
diastereoisomeric products undergo rapid epimerization due
to acidic hydrogens at C-2 and C-4 atoms. On the contrary,
the crystalline phosphonates 3d and 3e were isolated as
inseparable mixtures of diastereoisomers, each in a 1:0.35
ratio.
NO2
Figure 1. Conformation of the tert-butyl (2R*,3R*,4R*)-2-diethoxyphos-
phoryl-4-nitro-3-(4-nitrophenyl)pentanoate (4a).
single diastereoisomers. The assignment of the relative con-
figuration of the acids 5a–e and 6a–e was based on compar-
ison of their NMR spectral data with those of the respective
tert-butyl esters 3a–e and 4a–e. The acids displayed similar
values of the coupling constants JH2–H3 and JP–Cipso to
those observed for the esters 3a–e and 4a–c. Thus, the
relative configuration (2R*,3R*) and (2R*,3R*,4R*) could
be assigned to the acids 5a–e and 6a–e, respectively.
3
3
The relative stereochemistry of the stereogenic centers C-2
and C-3 in the phosphonates 3a–c and 4a–e was assigned
1
to be (2R*,3R*) on the basis of H and 13C NMR data.
3
The values of coupling constants JH2–H3¼10.6–12.2 Hz
The availability of the requisite nitroalkanoic acids 5a–e and
6a–e allowed us to attempt their conversion into 1-hydroxy-
succinimides 8a–e and 4-oxoalkanoic acids 9a–e, re-
spectively, by the spontaneous Nef reaction. After much
experimentation, we found that heating the 4-nitrobutanoic
acids 5a–e in boiling water for 40–70 min was optimal,
and provided the desired 1-hydroxysuccinimides 8a–e in ex-
cellent yields (Scheme 2 and Table 2). A noteworthy feature
of the Nef reaction is that the formation of the N-hydroxy-
succinamic acids 7a–e followed by their ring closure and
3
and JP–Cipso¼14.5–16.4 Hz indicate that the phosphonates
exist almost exclusively as a single conformers having anti-
planarly oriented phenyl and phosphoryl groups as well as
H-2 and H-3 atoms.19–22
The relative stereochemistry of the phosphonate 4a was
unequivocally determined to be (2R*,3R*,4R*) by X-ray
crystallographic analysis.23 It is worth noting that the phos-
phonate 4a exists in a fully extended zig–zag conformation
having the phosphoryl and 4-nitrophenyl groups in anti-
planar, and 4-nitrophenyl and methyl groups in gauche posi-
tions (Fig. 1). By analogy with the above results the relative
configuration of the adducts 4b–e was assigned to be
(2R*,3R*,4R*).
O
O
O
O
(EtO)2P
COOH
NHOH
(EtO)2P
COOH
NO2
(EtO)2P
a
N
OH
Ar
Ar
Ar
O
O
Deprotection of the tert-butyl alkanoates 3a–e and 4a–e with
CF3COOH afforded crystalline alkanoic acids 5a–e and
6a–e, respectively. Notably all the acids were obtained as
(2R*,3R*)-5a-e
7a-e
(3R*,4S*)-8a-e
Scheme 2. Reagent and condition: (a) H2O, reflux.

H. Krawczyk et al. / Tetrahedron 62 (2006) 9135–9145
Table 2. 1-Hydroxysuccinimides 8 and 4-oxoalkanoates 10 prepared
9137
Next, we focused our attention on converting 4-nitropenta-
noic acids 6a–e to the target 4-oxopentanoic acids 9a–e
(Scheme3). TheNef reactionproceededeffectivelyinboiling
water and it was completed within 1–2 h. The 4-oxoalkanoic
acids 9a–e were then isolated as crystalline dicyclohexyl-
ammonium salts 10a–e in good overall yields (Table 2).
Ar
8
10
Yield [%] Reaction
time [min]
Yield [%] Reaction
time [min]
a
b
c
4-NO2–C6H4–
4-Br–C6H4–
4-CH3–C6H4–
60
67
68
40
55
70
70
70
56
50
62
120
120
120
60
O
O
O
d
4-CH3O–C6H4– 64
(EtO)2P
COOH
O
(EtO)2P
COO NH2cHex2
O
(EtO)2P
COOH
NO2
O
a
b
e
79
60
59
90
O
Ar
Ar
Ar
(2R*,3S*)-10a-e
loss of water occurs with epimerization, giving 1-hydroxy-
succinimides 8a–e as thermodynamically stable trans iso-
mers, exclusively.
(2R*,3R*,4R*)-6a-e
9a-e
10d de = 62%
10e de = 72%
Scheme 3. Reagents and conditions: (a) H2O, reflux and (b) cHex2NH
(1.1 equiv), CH2Cl2, rt.
Spectroscopic studies were not useful in determining the ste-
reochemistry of imides 8a–e. X-ray crystallographic analy-
sis conducted on the imide 8b revealed that the phosphoryl
and aryl groups are in trans relationship and allowed us to as-
sign the (3R*,4S*) relative stereochemistry to the products
8a–e (Fig. 2). In this context it is also worth noting that
The stereochemistry of products 10a–e was similar to that
observed for hydroxyimides 8a–e. The dicyclohexylammo-
nium alkanoates 10a–c were formed as (2R*,3S*) diastereo-
isomers, exclusively. A notable exception is represented by
the products 10d and 10e that are formed as mixtures of dia-
stereoisomers of (2R*,3S*) and (2R*,3R*) in ratios 81:19
and 86:14, respectively. The assignment of the relative con-
figuration was based on 1H and 13C NMR data. It is reason-
able to assume that the phosphonates (2R*,3S*)-10a–e
are single conformers with the phosphoryl and acyl
groups (3JP–C]O¼18.2–19.6 Hz) as well as H-2 and H-3
(3JH2–H3¼11.3–11.8 Hz) antiplanar.
3
the values of coupling constant JP–H4¼18.0–18.1 Hz ob-
1
served in H NMR spectra of 8a and 8b are consistent
with the synperiplanar arrangement of the phosphorus and
H-4 atoms. The 1-hydroxysuccinimide ring in the crystal
structure of 8b is virtually planar. Deviations from the
least-squares mean plane calculated for all endocyclic non-
˚
hydrogen atoms are smaller than 0.03 A. On the contrary
to the unsubstituted N-hydroxysuccinimide molecule, as re-
ported by Jones,24 bond lengths of the equivalent endocyclic
C–N and C–C bonds are practically equal [N–C3 1.379(5),
3. Conclusions
˚
N–C4 1.372(5), C2–C3 1.524(5), C1–C4 1.517(5) A]. In
In conclusion, we have demonstrated that the Nef reaction of
primary and secondary 3-aryl-2-(diethoxyphosphoryl)-4-
nitroalkanoic acids is assisted by intramolecular catalysis. This
reaction provides a general and an efficient methodology
for the preparation of the corresponding 3-(diethoxyphos-
phoryl)-1-hydroxysuccinimides and 2-(diethoxyphosphoryl)-
4-oxoalkanoic acids in a highly stereoselective manner.
the crystal, molecules are linked into centrosymmetric
dimers through the hydrogen bonds between the hydroxyl
and phosphoryl groups. The respective interatomic O1/O4
˚
[1ꢀx, 1ꢀy, 1ꢀz] distance is 2.599(5) A. The exocyclic
carbonyl bonds are quite short [C3]O2 1.203(4), C4]O3
˚
1.197(4) A], when compared to the standard values reported
25
˚
for amides and g-lactams 1.234 and 1.235 A, respectively
and are not involved in the hydrogen bonding.
4. Experimental
4.1. General
NMR spectra were recorded on a Bruker DPX 250 instru-
1
ment at 250.13 MHz for H and 62.9 MHz for 13C and
101.3 MHz for 31P NMR using tetramethylsilane as an inter-
nal and 85% H3PO4 as an external standard. The multiplicity
of carbons was determined by DEPTexperiments. IR spectra
were measured on a Specord M80 (Zeiss) instrument. Ele-
mental analyses were performed on a Perkin–Elmer PE
2400 analyzer. Melting points were determined in open
capillaries and are uncorrected. Acrylic acids 1a–e were
prepared according to the literature procedure.17
4.2. General procedure for the preparation of tert-butyl
(E)-3-aryl-2-(diethoxyphosphoryl)acrylates 2a–e
Concentrated sulfuric acid (0.98 g, 10 mmol) was added to a
stirred suspension of magnesium sulfate (6.00 g, 50 mmol)
in CH2Cl2 (40 mL) and the resulting mixture was stirred at
Figure 2. View of 8b with atom numbering. Displacement ellipsoids were
drawn at the 50% probability level.

9138
H. Krawczyk et al. / Tetrahedron 62 (2006) 9135–9145
3
room temperature for 15 min. Acrylic acid 1 (10 mmol) and
tert-butyl alcohol (2.96 g, 40 mmol) were then added. The
mixture was stoppered tightly and was stirred for an appro-
priate period of time (shown in Table 1) at room temperature.
The reaction progress was occasionally monitored with
31P NMR. When the progress of the reaction was no longer
observed, saturated NaHCO3 solution was added (50 mL).
The organic layer was separated, washed with water
(2ꢁ20 mL), and dried over MgSO4. Evaporation of the
solvent under reduced pressure afforded a crude product,
which was purified by column chromatography (eluent:
ethyl acetate/hexane 2:1).
1H NMR (CDCl3): d¼1.37 (t, 6H, JHH¼7.0 Hz,
2ꢁCH3CH2OP), 1.53 (s, 9H, C(CH3)3), 4.09–4.24 (m, 4H,
2ꢁCH3CH2OP), 6.00 (s, 2H, CH2O2Ph), 6.80 (d, 1H,
3JHH¼8.5 Hz, CHAr), 7.01 (d, 1H, JHH¼8.5 Hz, CHAr),
3
7.04 (s, 1H, CHAr), 7.43 (d, 1H, 3JHP¼24.5 Hz, ArCH]C).
Anal. calcd for C18H25O7P: C, 56.25; H, 6.56. Found: C,
56.34; H, 6.64.
4.3. General procedure for the preparation of tert-butyl
3-aryl-2-(diethoxyphosphoryl)-4-nitroalkanoates 3a–e
and 4a–e
To a solution of a corresponding tert-butyl acrylate 2
(5 mmol) in nitromethane (20 mL) or nitroethane (10 mL)
was added potassium tert-butoxide (280 mg, 2.5 mmol).
The reaction mixture was left at room temperature for an
appropriate period of time. The reaction progress was
occasionally monitored with 31P NMR. After the acrylate
2 completely reacted the solvent was evaporated and residue
was taken up in CH2Cl2 (25 mL), washed with H2O
(2ꢁ15 mL), and dried over MgSO4. Evaporation of the
solvent under reduced pressure afforded a crude product,
which was purified by crystallization from diethyl ether to
give pure alkanoates 3 and 4.
4.2.1. tert-Butyl (E)-2-(diethoxyphosphoryl)-3-(4-nitro-
phenyl)acrylate (2a). 2.70 g, 82% yield, yellow oil;
Rf¼0.5 (ethyl acetate/hexane 2:1); IR (film): 1720, 1348,
1
1256, 1156 cmꢀ1
;
31P NMR (CDCl3): d¼12.98; H NMR
3
(CDCl3): d¼1.39 (t, 3H, JHH¼7.0 Hz, CH3CH2OP), 1.40
3
(t, 3H, JHH¼7.0 Hz, CH3CH2OP), 1.48 (s, 9H, C(CH3)3),
3
4.15–4.28 (m, 4H, 2ꢁCH3CH2OP), 7.62 (d, 1H, JHP
¼
3
23.8 Hz, ArCH]C), 7.63 (d, 2H, JHH¼8.8 Hz, 2ꢁCHAr),
3
8.24 (d, 2H, JHH¼8.8 Hz, 2ꢁCHAr). Anal. calcd for
C17H24NO7P: C, 52.99; H, 6.28; N, 3.63. Found: C, 53.11;
H, 6.17; N, 3.51.
4.2.2. tert-Butyl (E)-3-(4-bromophenyl)-2-(diethoxyphos-
phoryl)acrylate (2b). 3.56 g, 85% yield, pale yellow oil;
4.3.1. tert-Butyl 2-(diethoxyphosphoryl)-4-nitro-3-(4-
nitrophenyl)butanoate (3a). Crude product: 31P NMR
(CDCl3): d¼19.02, 19.32 (0.42:1); (2R*,3R*)-3a: (2.01 g,
90% yield), white crystals, mp 164–168 ꢂC; IR (CCl4):
Rf¼0.5 (ethyl acetate/hexane 2:1); IR (film): 1716, 1368,
1
1252, 1032 cmꢀ1
;
31P NMR (CDCl3): d¼14.39; H NMR
3
(CDCl3): d¼1.37 (t, 6H, JHH¼7.0 Hz, 2ꢁCH3CH2OP),
1.49 (s, 9H, C(CH3)3), 4.10–4.25 (m, 4H, 2ꢁCH3CH2OP),
1736, 1552, 1348, 1280, 1160, 1020 cmꢀ1 31P NMR
;
(CDCl3): d¼19.32; 1H NMR (CDCl3): d¼1.17 (s, 9H,
3
3
3
7.35 (d, 2H, JHH¼8.8 Hz, 2ꢁCHAr), 7.49 (d, 1H, JHP
¼
C(CH3)3), 1.36 (t, 3H, JHH¼7.0 Hz, CH3CH2OP), 1.39 (t,
3
3
2
24.0 Hz, ArCH]C), 7.51 (d, 2H, JHH¼8.8 Hz, 2ꢁCHAr).
Anal. calcd for C17H24BrO5P: C, 48.70; H, 5.77. Found:
C, 48.79; H, 5.65.
3H, JHH¼7.0 Hz, CH3CH2OP), 3.35 (dd, 1H, JHP¼
3
20.1 Hz, JHH¼11.8 Hz, PCHCOOt-Bu), 4.18–4.30 (m,
2
5H, 2ꢁCH3CH2OP, CHAr), 4.75 (dd, 1H, JHH¼13.5 Hz,
3JHH¼10.6 Hz, ArCHCHAHBNO2), 5.27 (dd, 1H,
3
4.2.3. tert-Butyl (E)-2-(diethoxyphosphoryl)-3-(4-methyl-
phenyl)acrylate (2c). 3.11 g, 88% yield, pale yellow oil;
2JHH¼13.5 Hz, JHH¼4.1 Hz, ArCHCHAHBNO2), 7.44 (d,
3
3
2H, JHH¼8.8 Hz, 2ꢁCHAr), 8.20 (d, 2H, JHH¼8.8 Hz,
3
Rf¼0.5 (ethyl acetate/hexane 2:1); IR (film): 1716, 1368,
2ꢁCHAr); 13C NMR (CDCl3): d¼16.11 (d, JCP¼5.4 Hz,
1
3
1256, 1024 cmꢀ1
;
31P NMR (CDCl3): d¼15.37; H NMR
CH3CH2OP), 16.19 (d, JCP¼5.2 Hz, CH3CH2OP), 27.23
3
2
(CDCl3): d¼1.36 (t, 6H, JHH¼7.1 Hz, 2ꢁCH3CH2OP),
(C(CH3)3), 42.22 (d, JCP¼3.4 Hz, ArCH), 49.24 (d,
2
1.50 (s, 9H, C(CH3)3), 2.36 (s, 3H, CH3Ph), 4.13–4.20 (m,
4H, 2ꢁCH3CH2OP), 7.17 (d, 2H, JHH¼8.0 Hz, 2ꢁCHAr),
1JCP¼128.5 Hz, PCHCOOt-Bu), 63.32 (d, JCP¼3.0 Hz,
3
2
CH3CH2OP), 63.42 (d, JCP¼3.9 Hz, CH3CH2OP), 77.89
3
7.39 (d, 2H, JHH¼8.0 Hz, 2ꢁCHAr), 7.52 (d, 1H,
(CH2NO2), 82.77 (C(CH3)3), 123.61 (CHAr), 129.27
(CHAr), 144.55 (d, JCP¼15.7 Hz, CAr), 146.91 (CAr),
3JHP¼24.5 Hz, ArCH]C). Anal. calcd for C18H27O5P: C,
3
3
61.01; H, 7.68. Found: C, 61.12; H, 7.79.
165.07 (d, JCP¼6.0 Hz, PCHCOOt-Bu). Anal. calcd for
C18H27N2O9P: C, 48.43; H, 6.10; N, 6.28. Found: C,
48.53; H, 6.18; N, 6.20.
4.2.4. tert-Butyl (E)-2-(diethoxyphosphoryl)-3-(4-meth-
oxyphenyl)acrylate (2d). 3.03g, 82% yield, pale yellow
oil; Rf¼0.5 (ethyl acetate/hexane 2:1); IR (film): 1716,
4.3.2. tert-Butyl 3-(4-bromophenyl)-2-(diethoxyphos-
phoryl)-4-nitrobutanoate (3b). Crude product: 31P NMR
(CDCl3): d¼19.63, 19.99 (0.38:1); (2R*,3R*)-3b: (1.61 g,
67% yield), white crystals, mp 144–146 ꢂC; IR (CCl4):
1604, 1512, 1368, 1260, 1152, 1028 cmꢀ1 31P NMR
;
(CDCl3): d¼16.30; 1H NMR (CDCl3): d¼1.36 (t, 6H,
3JHH¼7.0 Hz, 2ꢁCH3CH2OP), 1.52 (s, 9H, C(CH3)3), 3.84
(s, 3H, CH3OPh), 4.08–4.22 (m, 4H, 2ꢁCH3CH2OP), 6.88
(d, 2H, 3JHH¼8.8 Hz, 2ꢁCHAr), 7.47 (d, 2H, 3JHH¼8.8 Hz,
1736, 1552, 1276, 1240, 1224, 1160, 1060, 992, 976 cmꢀ1
;
1
31P NMR (CDCl3): d¼19.99; H NMR (CDCl3): d¼1.17
3
3
2ꢁCHAr), 7.49 (d, 1H, JHP¼24.5 Hz, ArCH]C). Anal.
(s, 9H, C(CH3)3), 1.38 (t, 3H, JHH¼7.0 Hz, CH3CH2OP),
calcd for C18H27O6P: C, 58.37; H, 7.35. Found: C, 58.28;
H, 7.27.
1.40 (t, 3H, 3JHH¼7.0 Hz, CH3CH2OP), 3.28 (dd, 1H, 2JHP
¼
19.6 Hz, 3JHH¼11.9 Hz, PCHCOOt-Bu), 4.01–4.15 (m, 1H,
CHAr), 4.18–4.29 (m, 4H, 2ꢁCH3CH2OP), 4.66 (dd, 1H,
3
4.2.5. tert-Butyl (E)-2-(diethoxyphosphoryl)-3-(3,4-
methylenedioxyphenyl)acrylate (2e). 3.49 g, 91% yield,
pale yellow oil; Rf¼0.5 (ethyl acetate/hexane 2:1); IR (film):
2JHH¼13.2 Hz, JHH¼10.7 Hz, ArCHCHAHBNO2), 5.20
2
3
(dd, 1H, JHH¼13.2 Hz, JHH¼4.1 Hz, ArCHCHAHBNO2),
3
7.13 (d, 2H, JHH¼8.5 Hz, 2ꢁCHAr), 7.44 (d, 2H,
1716, 1368, 1256, 1028 cmꢀ1
;
31P NMR (CDCl3): d¼15.56;
3JHH¼8.5 Hz, 2ꢁCHAr); 13C NMR (CDCl3): d¼16.03

H. Krawczyk et al. / Tetrahedron 62 (2006) 9135–9145
9139
3
3
3
(d, JCP¼5.8 Hz, CH3CH2OP), 16.15 (d, JCP¼5.6 Hz,
minor), 128.64 (d, JCP¼16.0 Hz, CAr, major), 128.68
2
3
CH3CH2OP), 27.14 (C(CH3)3), 42.03 (d, JCP¼3.7 Hz,
(CHAr, minor), 129.02 (CHAr, major), 129.11 (d, JCP
¼
1
ArCH), 49.49 (d, JCP¼128.1 Hz, PCHCOOt-Bu), 63.07
11.8 Hz, CAr, minor), 159.07 (CAr), 165.30 (d, 3JCP¼5.2 Hz,
PCHCOOt-Bu, major), 166.33 (d, 3JCP¼4.1 Hz, PCHCOOt-
Bu, minor). Anal. calcd for C19H30NO8P: C, 52.90; H, 7.01;
N, 3.25. Found: C, 52.99; H, 7.12; N, 3.36.
2
2
(d, JCP¼3.2 Hz, CH3CH2OP), 63.18 (d, JCP¼2.4 Hz,
CH3CH2OP), 78.26 (CH2NO2), 82.30 (C(CH3)3), 121.91
(CAr), 129.76 (CHAr), 131.55 (CHAr), 135.95 (d, JCP
3
¼
3
15.9 Hz, CAr), 165.18 (d, JCP¼7.0 Hz, PCHCOOt-Bu).
Anal. calcd for C18H27BrNO7P: C, 45.01; H, 5.67; N, 2.92.
Found: C, 45.11; H, 5.71; N, 2.80.
4.3.5. tert-Butyl 2-(diethoxyphosphoryl)-3-(3,4-methylene-
dioxyphenyl)-4-nitrobutanoate (3e). 1.62 g, 73% yield,
white crystals, mp 83–86 ꢂC; IR (CCl4): 1732, 1556, 1248,
4.3.3. tert-Butyl 2-(diethoxyphosphoryl)-3-(4-methyl-
phenyl)-4-nitrobutanoate (3c). Crude product: 31P NMR
(CDCl3): d¼20.13, 20.61 (0.39:1); (2R*,3R*)-3c: (1.66 g,
80% yield), white crystals, mp 79–81 ꢂC; IR (CCl4): 1728,
1148, 1044 cmꢀ1
;
31P NMR (CDCl3): d¼19.97, 20.35
(0.35:1); 1H NMR (CDCl3): d¼1.21 (s, 9H, C(CH3)3,
major), 1.30 (t, 3H, 3JHH¼7.0 Hz, CH3CH2OP, minor), 1.32
3
(t, 3H, JHH¼7.0 Hz, CH3CH2OP, minor), 1.38 (t, 3H,
1556, 1248, 1156, 1024 cmꢀ1
;
31P NMR (CDCl3):
3JHH¼7.2 Hz, CH3CH2OP, major), 1.41 (t, 3H, JHH
¼
3
d¼20.61; 1H NMR (CDCl3): d¼1.14 (s, 9H, C(CH3)3),
7.2 Hz, CH3CH2OP, major), 1.46 (s, 9H, C(CH3)3, minor),
3
2
3
1.37 (t, 3H, JHH¼7.0 Hz, CH3CH2OP), 1.41 (t, 3H,
3.20 (dd, 1H, JHP¼23.2 Hz, JHH¼6.0 Hz, PCHCOOt-Bu,
3JHH¼7.0 Hz, CH3CH2OP), 2.29 (s, 3H, CH3Ph), 3.30 (dd,
minor), 3.24 (dd, 1H, JHP¼19.5 Hz, JHH¼12.0 Hz,
PCHCOOt-Bu, major), 3.95–4.30 (m, 5H, 2ꢁCH3CH2OP,
CHAr), 4.63 (dd, 1H, 2JHH¼13.0 Hz, 3JHH¼10.8 Hz, ArCH-
2
3
2
3
1H, JHP¼19.3 Hz, JHH¼12.0 Hz, PCHCOOt-Bu), 3.98–
4.09 (m, 1H, CHAr), 4.17–4.31 (m, 4H, 2ꢁCH3CH2OP),
2
3
3
4.66 (dd, 1H, JHH¼12.8 Hz, JHH¼10.8 Hz, ArCH-
CHAHBNO2, major), 5.06 (d, 1H, JHH¼4.2 Hz, ArCH-
2
3
CHAHBNO2), 5.18 (dd, 1H, JHH¼12.8 Hz, JHH¼4.0 Hz,
ArCHCHAHBNO2), 7.10 (s, 4H, 4ꢁCHAr); 13C NMR
(CDCl3): d¼15.98 (d, 3JCP¼6.0 Hz, CH3CH2OP), 16.08 (d,
3JCP¼5.9 Hz, CH3CH2OP), 20.67 (CH3Ph), 27.02
CH2NO2, minor), 5.09 (s, 1H, ArCHCH2NO2, minor), 5.17
2
3
(dd, 1H, JHH¼13.0 Hz, JHH¼4.0 Hz, ArCHCHAHBNO2,
major), 5.93 (s, 2H, CH2O2Ph, major), 5.94 (s, 2H, CH2O2Ph,
minor), 6.70–6.74 (m, 3H, 3ꢁCHAr); 13C NMR (CDCl3):
(C(CH3)3), 42.20 (d, 2JCP¼3.8 Hz, ArCH), 49.74 (d, 1JCP
¼
d¼16.00 (d, JCP¼5.6 Hz, CH3CH2OP), 16.08 (d,
3
127.6 Hz, PCHCOOt-Bu), 62.88 (d, 2JCP¼3.4 Hz,
3JCP¼5.7 Hz, CH3CH2OP), 27.15 (C(CH3)3, major), 27.49
2
2
CH3CH2OP), 62.93 (d, JCP¼3.7 Hz, CH3CH2OP), 78.70
(C(CH3)3, minor), 41.55 (d, JCP¼3.5 Hz, ArCH, minor),
2
1
(CH2NO2), 81.86 (C(CH3)3), 127.76 (CHAr), 128.96
(CHAr), 133.58 (d, JCP¼15.8 Hz, CAr), 137.51 (CAr),
42.36 (d, JCP¼3.3 Hz, ArCH, major), 49.87 (d, JCP
¼
3
1
127.4 Hz, PCHCOOt-Bu, major), 50.58 (d, JCP
129.1 Hz, PCHCOOt-Bu, minor), 62.53 (d, JCP¼7.0 Hz,
¼
3
2
165.28 (d, JCP¼5.4 Hz, PCHCOOt-Bu). Anal. calcd for
2
C19H30NO7P: C, 54.93; H, 7.28; N, 3.37. Found: C, 54.77;
H, 7.37; N, 3.26.
CH3CH2OP, minor), 62.79 (d, JCP¼5.4 Hz, CH3CH2OP,
2
minor), 62.92 (d, JCP¼3.6 Hz, CH3CH2OP, major),
2
63.02 (d, JCP¼2.3 Hz, CH3CH2OP, major), 77.16 (d,
4.3.4. tert-Butyl 2-(diethoxyphosphoryl)-3-(4-methoxy-
phenyl)-4-nitrobutanoate (3d). 1.21 g, 56% yield, white
crystals, mp 93–95 ꢂC; IR (CCl4): 1728, 1556, 1252, 1148,
3JCP¼8.1 Hz, CH2NO2, minor), 78.67 (CH2NO2, major),
81.97 (C(CH3)3, major), 82.76 (C(CH3)3, minor), 100.91
(CH2O2Ph), 107.78 (CHAr, minor), 107.99 (CHAr, major),
108.09 (CHAr), 121.05 (CHAr, minor), 121.57 (CHAr,
1024 cmꢀ1
;
31P NMR (CDCl3): d¼20.13, 20.55 (0.35:1);
1H NMR (CDCl3): d¼1.16 (s, 9H, C(CH3)3, major), 1.28 (t,
major), 130.27 (d, JCP¼16.1 Hz, CAr, major), 130.98 (d,
3
3
3H, JHH¼7.0 Hz, CH3CH2OP, minor), 1.30 (t, 3H,
3JCP¼11.8 Hz, CAr, minor), 147.09 (CAr), 147.51 (CAr,
3JHH¼7.0 Hz, CH3CH2OP, minor), 1.38 (t, 3H, JHH
¼
major), 147.68 (CAr, minor), 165.22 (d, JCP¼5.6 Hz,
3
2
3
7.2 Hz, CH3CH2OP, major), 1.41 (t, 3H, JHH¼7.2 Hz,
PCHCOOt-Bu, major), 166.28 (d, 2JCP¼3.8 Hz, PCHCOOt-
Bu, minor). Anal. calcd for C19H28NO9P: C, 51.24; H, 6.34;
N, 3.14. Found: C, 51.33; H, 6.22; N, 3.21.
CH3CH2OP, major), 1.46 (s, 9H, C(CH3)3, minor), 3.23
2
3
(dd, 1H, JHP¼23.2 Hz, JHH¼6.2 Hz, PCHCOOt-Bu,
2
3
minor), 3.28 (dd, 1H, JHP¼19.2 Hz, JHH¼12.0 Hz,
PCHCOOt-Bu, major), 3.76 (s, 3H, CH3OPh, major), 3.78
(s, 3H, CH3OPh, minor), 3.98–4.29 (m, 5H, 2ꢁCH3CH2OP,
4.3.6. tert-Butyl 2-(diethoxyphosphoryl)-4-nitro-3-(4-
nitrophenyl)pentanoate (4a). Crude product: 31P NMR
(CDCl3): d¼19.30, 19.34, 19.96, 20.43 (1:0.31:0.28:0.62);
(2R*,3R*,4R*)-4a: (1.61 g, 70% yield), white crystals, mp
216–218 ꢂC; IR (CCl4): 1724, 1544, 1348, 1248, 1156,
2
3
CHAr), 4.64 (dd, 1H, JHH¼13.0 Hz, JHH¼11.0 Hz,
3
ArCHCHAHBNO2, major), 5.07 (d, 2H, JHH¼7.5 Hz,
ArCHCH2NO2, minor), 5.18 (dd, 1H, 2JHH¼13.0 Hz, 3JHH
¼
4.0 Hz, ArCHCHAHBNO2, major), 6.79–6.86 (m, 2H,
2ꢁCHAr), 7.12–7.20 (m, 2H, 2ꢁCHAr); 13C NMR
(CDCl3): d¼15.98 (d, 3JCP¼5.4 Hz, CH3CH2OP), 16.06 (d,
3JCP¼5.6 Hz, CH3CH2OP), 27.06 (C(CH3)3, major), 27.46
1020 cmꢀ1
;
31P NMR (CDCl3): d¼19.30; 1H NMR
(CDCl3): d¼1.17 (s, 9H, C(CH3)3), 1.38–1.44 (m, 6H,
3
2ꢁCH3CH2OP), 1.42 (d, 3H, JHH¼6.8 Hz, CH3CHNO2),
2
3
3.37 (dd, 1H, JHP¼21.0 Hz, JHH¼11.8 Hz, PCHCOOt-
Bu), 4.17–4.30 (m, 4H, 2ꢁCH3CH2OP), 4.41 (ddd, 1H,
3JHH¼11.8, 3JHP¼8.6 Hz, 3JHH¼4.7 Hz, Ar–CH), 5.42 (dq,
2
(C(CH3)3, minor), 41.11 (d, JCP¼2.6 Hz, ArCH, minor),
2
1
41.89 (d, JCP¼3.5 Hz, ArCH, major), 49.84 (d, JCP
¼
127.4 Hz, PCHCOOt-Bu, major), 50.58 (d, 1JCP¼129.4 Hz,
1H, JHH¼6.8 Hz, JHH¼4.7 Hz, CH3CHNO2), 7.36 (d,
3
3
3
3
PCHCOOt-Bu, minor), 54.85 (CH3OPh), 62.44 (d,
2H, JHH¼8.8 Hz, 2ꢁCHAr), 8.18 (d, 2H, JHH¼8.8 Hz,
2ꢁCHAr); 13C NMR (CDCl3): d¼12.60 (CH3CHNO2),
16.19 (2ꢁCH3CH2OP), 27.22 (C(CH3)3), 47.06 (ArCH),
2JCP¼7.3 Hz, CH3CH2OP, minor), 62.69 (d, JCP¼6.9 Hz,
2
2
CH3CH2OP, minor), 62.91 (d, JCP¼6.0 Hz, CH3CH2OP,
3
1
major), 77.27 (d, JCP¼8.4 Hz, CH2NO2, minor), 78.75
48.34 (d, JCP¼129.5 Hz, PCHCOOt-Bu), 63.32 (d,
2
(CH2NO2, major), 81.84 (C(CH3)3, major), 82.61
(C(CH3)3, minor), 113.69 (CHAr, major), 113.84 (CHAr,
2JCP¼5.7 Hz, CH3CH2OP), 63.40 (d, JCP¼5.0 Hz,
3
CH3CH2OP), 82.82 (d, JCP¼7.0 Hz, CH3CHNO2), 83.01

9140
H. Krawczyk et al. / Tetrahedron 62 (2006) 9135–9145
3
(C(CH3)3), 123.21 (CHAr), 130.26 (CHAr), 141.98 (d,
3JCP¼14.5 Hz, CAr), 147.58 (CAr), 165.21 (PCHCOOt-Bu).
Anal. calcd for C19H29N2O9P: C, 49.56; H, 6.35; N, 6.08.
Found: C, 49.67; H, 6.47; N, 6.00.
3JHH¼8.8 Hz, 2ꢁCHAr), 7.03 (d, 2H, JHH¼8.8 Hz,
2ꢁCHAr); 13C NMR (CDCl3): d¼12.11 (CH3CHNO2),
3
3
16.09 (d, JCP¼4.8 Hz, CH3CH2OP), 16.17 (d, JCP
¼
¼
2
5.7 Hz, CH3CH2OP), 27.13 (C(CH3)3), 46.68 (d, JCP
1
3.3 Hz, ArCH), 48.89 (d, JCP¼128.7 Hz, PCHCOOt-Bu),
2
4.3.7. tert-Butyl 3-(4-bromophenyl)-2-(diethoxyphos-
phoryl)-4-nitropentanoate (4b). Crude product: 31P NMR
54.98 (CH3OPh), 62.94 (d, JCP¼7.8 Hz, CH3CH2OP),
2
63.06 (d, JCP¼7.4 Hz, CH3CH2OP), 82.00 (C(CH3)3),
3
(CDCl3):
d¼19.97,
20.77,
21.23
(1:0.15:0.39);
(2R*,3R*,4R*)-4b: (1.63 g, 66% yield), white crystals, mp
83.48 (CH3CHNO2), 113.45 (CHAr), 125.95 (d, JCP
16.4 Hz, CAr), 130.14 (CHAr), 159.26 (CAr), 165.54 (d,
¼
172–174 ꢂC; IR (CCl4): 1724, 1548, 1392, 1288, 1248,
2JCP¼6.0 Hz,
PCHCOOt-Bu).
Anal.
calcd
for
1156, 1024 cmꢀ1
;
31P NMR (CDCl3): d¼19.97; H NMR
C20H32NO8P: C, 53.93; H, 7.24; N, 3.14. Found: C, 53.77;
H, 7.35; N, 3.01.
1
(CDCl3): d¼1.16 (s, 9H, C(CH3)3), 1.34–1.44 (m, 6H,
3
2ꢁCH3CH2OP), 1.40 (d, 3H, JHH¼6.5 Hz, CH3CHNO2),
2
3
3.33 (dd, 1H, JHP¼20.5 Hz, JHH¼12.0 Hz, PCHCOOt-
Bu), 4.17–4.32 (m, 5H, 2ꢁCH3CH2OP, Ar–CH), 5.34 (dq,
4.3.10. tert-Butyl 2-(diethoxyphosphoryl)-3-(3,4-methyl-
enedioxyphenyl)-4-nitropentanoate (4e). Crude product:
31P NMR (CDCl3): d¼20.34, 21.04, 21.53 (1:0.14:0.39);
(2R*,3R*,4R*)-4e: (1.17 g, 51% yield), white crystals, mp
101–107 ꢂC; IR (CCl4): 1728, 1552, 1488, 1444, 1392,
3
3
1H, JHH¼6.5 Hz, JHH¼4.5 Hz, CH3CHNO2), 7.02 (d,
3
3
2H, JHH¼8.5 Hz, 2ꢁCHAr), 7.43 (d, 2H, JHH¼8.5 Hz,
2ꢁCHAr); 13C NMR (CDCl3): d¼12.29 (CH3CHNO2),
16.09 (d, 3JCP¼3.4 Hz, CH3CH2OP), 16.19 (d, 3JCP¼3.3 Hz,
1368, 1256, 1160, 1032 cmꢀ1
;
31P NMR (CDCl3):
2
CH3CH2OP), 27.14 (C(CH3)3), 46.79 (d, JCP¼3.0 Hz,
d¼20.34; 1H NMR (CDCl3): d¼1.19 (s, 9H, C(CH3)3),
1
ArCH), 48.52 (d, JCP¼129.1 Hz, PCHCOOt-Bu), 63.04
1.35–1.46 (m, 9H, 2ꢁCH3CH2OP, CH3CHNO2), 3.29 (dd,
2
2
2
3
(d, JCP¼7.3 Hz, CH3CH2OP), 63.20 (d, JCP¼6.4 Hz,
CH3CH2OP), 82.36 (C(CH3)3), 83.10 (CH3CHNO2),
122.18 (CAr), 130.77 (CHAr), 131.25 (CHAr), 133.31 (d,
1H, JHP¼20.0 Hz, JHH¼12.2 Hz, PCHCOOt-Bu), 4.18–
4.31 (m, 5H, 2ꢁCH3CH2OP, Ar–CH), 5.29 (dq, 1H,
3JHH¼6.5 Hz, JHH¼4.5 Hz, CH3CHNO2), 5.92–5.94 (m,
3
2
3
4
3JCP¼16.0 Hz, CAr), 165.32 (d, JCP¼6.3 Hz, PCHCOOt-
2H, CH2O2Ph), 6.57 (dd, 1H, JHH¼8.0 Hz, JHH¼1.8 Hz,
4
Bu). Anal. calcd for C19H29BrNO7P: C, 46.17; H, 5.19; N,
2.83. Found: C, 46.28; H, 5.27; N, 2.95.
CHAr), 6.62 (d, 1H, JHH¼1.8 Hz, CHAr), 6.72 (d, 1H,
3JHH¼8.0 Hz, CHAr); 13C NMR (CDCl3): d¼12.19
3
(CH3CHNO2), 16.11 (d, JCP¼5.9 Hz, CH3CH2OP), 16.19
3
4.3.8. tert-Butyl 2-(diethoxyphosphoryl)-3-(4-methyl-
phenyl)-4-nitropentanoate (4c). Crude product: 31P NMR
(CDCl3): d¼20.45, 20.63, 21.27, 21.91, (0.19:1:0.16:0.45);
(2R*,3R*,4R*)-4c: (1.05 g, 49% yield), white crystals, mp
(d, JCP¼4.2 Hz, CH3CH2OP), 27.21 (C(CH3)3), 47.09
1
(ArCH), 48.89 (d, JCP¼128.7 Hz, PCHCOOt-Bu), 62.99
2
2
(d, JCP¼7.9 Hz, CH3CH2OP), 63.12 (d, JCP¼7.0 Hz,
CH3CH2OP), 82.09 (C(CH3)3), 83.43 (CH3CHNO2),
100.98 (CH2O2Ph), 107.84 (CHAr), 109.29 (CHAr), 122.68
133–135 ꢂC; IR (CCl4): 1732, 1552, 1392, 1368, 1252,
1
3
1160, 1028 cmꢀ1
;
31P NMR (CDCl3): d¼20.63; H NMR
(CHAr), 127.63 (d, JCP¼16.4 Hz, CAr), 147.27 (CAr),
2
(CDCl3): d¼1.12 (s, 9H, C(CH3)3), 1.35–1.44 (m, 6H,
147.39 (CAr), 165.45 (d, JCP¼6.3 Hz, PCHCOOt-Bu).
3
2ꢁCH3CH2OP), 1.41 (d, 3H, JHH¼6.5 Hz, CH3CHNO2),
Anal. calcd for C20H30NO9P: C, 52.29; H, 6.58; N, 3.05.
Found: C, 52.20; H, 6.69; N, 3.17.
2
3
2.29 (s, 3H, CH3Ph), 3.36 (dd, 1H, JHP¼19.9 Hz, JHH
¼
12.2 Hz, PCHCOOt-Bu), 4.19–4.30 (m, 5H, 2ꢁCH3CH2OP,
3
3
Ar–CH), 5.32 (dq, 1H, JHH¼6.5 Hz, JHH¼4.4 Hz,
4.4. General procedure for the preparation of 3-aryl-2-
(diethoxyphosphoryl)-4-nitroalkanoic acids 5a–e and
6a–e
3
CH3CHNO2), 6.98 (d, 2H, JHH¼8.0 Hz, 2ꢁCHAr), 7.08
(d, 2H, JHH¼8.0 Hz, 2ꢁCHAr); 13C NMR (CDCl3): d¼
3
3
12.11 (CH3CHNO2), 16.09 (d, JCP¼5.5 Hz, CH3CH2OP),
16.18 (d, 3JCP¼5.2 Hz, CH3CH2OP), 20.80 (CH3Ph), 27.06
To a solution of a corresponding tert-butyl alkanoate 3 or 4
(2.5 mmol) in CH2Cl2 (5 mL) was added trifluoroacetic acid
(5 mL). The reaction mixture was left at room temperature
for 24 h. The solvent was evaporated and residue was taken
up in Et2O (15 mL) and left to crystallize. Filtration of the
crystals afforded pure alkanoic acids 5 and 6.
2
(C(CH3)3), 47.00 (d, JCP¼3.2 Hz, ArCH), 48.80 (d,
1JCP¼128.7 Hz, PCHCOOt-Bu), 62.94 (d, JCP¼7.6 Hz,
2
2
CH3CH2OP), 63.06 (d, JCP¼7.6 Hz, CH3CH2OP), 81.96
(C(CH3)3), 83.41 (CH3CHNO2), 128.73 (CHAr), 128.90
(CHAr), 130.95 (d, JCP¼15.7 Hz, CAr), 137.70 (CAr),
3
2
165.51 (d, JCP¼6.2 Hz, PCHCOOt-Bu). Anal. calcd for
C20H32NO7P: C, 55.94; H, 7.51; N, 3.26. Found: C, 55.77;
H, 7.64; N, 3.11.
4.4.1. (2R*,3R*)-2-(Diethoxyphosphoryl)-4-nitro-3-(4-
nitrophenyl)butanoic acid (5a). 878 mg, 90% yield, white
crystals, mp 149–151 ꢂC; IR (CCl4): 1728, 1552, 1352,
4.3.9. tert-Butyl 2-(diethoxyphosphoryl)-3-(4-methoxy-
phenyl)-4-nitropentanoate (4d). Crude product: 31P NMR
1224, 1152, 1020 cmꢀ1
;
31P NMR (acetone-d): d¼19.35;
3
1H NMR (acetone-d): d¼1.21 (t, 3H, JHH¼7.0 Hz,
3
(CDCl3):
(2R*,3R*,4R*)-4d: (1.29 g, 58% yield), white crystals, mp
d¼20.58,
21.00,
21.54
(1:0.14:0.41);
CH3CH2OP), 1.22 (t, 3H, JHH¼7.0 Hz, CH3CH2OP), 3.64
(dd, 1H, 2JHP¼20.8 Hz, 3JHH¼11.5 Hz, PCHCOOH), 4.04–
138–140 ꢂC; IR (CCl4): 1728, 1512, 1392, 1368, 1252,
4.25 (m, 5H, 2ꢁCH3CH2OP, CHAr), 4.93 (dd, 1H,
1160, 1024 cmꢀ1
;
31P NMR (CDCl3): d¼20.58; H NMR
2JHH¼13.5 Hz, JHH¼11.0 Hz, ArCHCHAHBNO2), 5.30
1
3
2
3
(CDCl3): d¼1.14 (s, 9H, C(CH3)3), 1.33–1.44 (m, 9H,
2ꢁCH3CH2OP, CH3CHNO2), 3.34 (dd, 1H, 2JHP¼20.0 Hz,
3JHH¼12.2 Hz, PCHCOOt-Bu), 3.77 (s, 3H, CH3OPh),
4.18–4.31 (m, 5H, 2ꢁCH3CH2OP, Ar–CH), 5.30 (dq, 1H,
(dd, 1H, JHH¼13.5 Hz, JHH¼4.1 Hz, ArCHCHAHBNO2),
3
7.63 (d, 2H, JHH¼8.8 Hz, 2ꢁCHAr), 8.07 (d, 2H,
3JHH¼8.8 Hz, 2ꢁCHAr); 13C NMR (acetone-d): d¼16.50
3
3
(d, JCP¼5.7 Hz, CH3CH2OP), 16.57 (d, JCP¼3.5 Hz,
3JHH¼6.5 Hz, JHH¼4.2 Hz, CH3CHNO2), 6.81 (d, 2H,
CH3CH2OP), 43.50 (d, JCP¼3.6 Hz, ArCH), 49.03 (d,
3
2

H. Krawczyk et al. / Tetrahedron 62 (2006) 9135–9145
9141
2
3
3
1JCP¼126.8 Hz, PCHCOOH), 64.07 (d, JCP¼6.4 Hz,
d¼16.48 (d, JCP¼5.5 Hz, CH3CH2OP), 16.56 (d, JCP¼
2
CH3CH2OP), 64.17 (d, JCP¼6.8 Hz, CH3CH2OP), 78.87
4.3 Hz, CH3CH2OP), 43.16 (d, 2JCP¼4.1 Hz, ArCH), 49.64
1
(CH2NO2), 124.28 (CHAr), 130.80 (CHAr), 146.57 (d,
3JCP¼15.5 Hz, CAr), 148.52 (CAr), 168.21 (d, 2JCP¼5.7 Hz,
PCHCOOH). Anal. calcd for C14H19N2O9P: C, 43.08; H,
4.91; N, 7.18. Found: C, 43.20; H, 4.79; N, 7.11.
(d, JCP¼126.0 Hz, PCHCOOH), 55.39 (CH3OPh), 64.02
(d, 2JCP¼6.5 Hz, 2ꢁCH3CH2OP), 79.67 (CH2NO2), 114.58
3
(CHAr), 130.24 (d, JCP¼12.8 Hz, CAr), 130.34 (CHAr),
2
160.16 (CAr), 168.39 (d, JCP¼5.4 Hz, PCHCOOH). Anal.
calcd for C15H22NO8P: C, 48.00; H, 5.91; N, 3.73. Found:
C, 48.11; H, 5.83; N, 3.82.
4.4.2. (2R*,3R*)-3-(4-Bromophenyl)-2-(diethoxyphos-
phoryl)-4-nitrobutanoic acid (5b). 848 mg, 80% yield,
white crystals, mp 128–130 ꢂC; IR (CCl4): 1732, 1556,
4.4.5. (2R*,3R*)-2-(Diethoxyphosphoryl)-3-(3,4-methyl-
enedioxyphenyl)-4-nitrobutanoic acid (5e). 914 mg, 94%
yield, white crystals, mp 138–140 ꢂC; IR (CCl4): 1716,
1220, 1172, 1012, 984 cmꢀ1
;
31P NMR (acetone-d):
d¼19.80; 1H NMR (acetone-d): d¼1.34 (dt, 3H, JHH
¼
3
7.1 Hz, 4JHP¼0.5 Hz, CH3CH2OP), 1.35 (dt, 3H,
1552, 1228, 1168, 1016 cmꢀ1 31P NMR (acetone-d):
;
3JHH¼7.1 Hz, JHP¼0.5 Hz, CH3CH2OP), 3.66 (dd, 1H,
d¼20.03; 1H NMR (acetone-d): d¼1.34 (t, 3H,
4
2JHP¼20.2 Hz, JHH¼11.7 Hz, PCHCOOH), 4.04–4.28 (m,
3JHH¼7.1 Hz, CH3CH2OP), 1.35 (t, 3H, JHH¼7.1 Hz,
3
3
2
2
3
5H, 2ꢁCH3CH2OP, CHAr), 4.94 (dd, 1H, JHH¼13.2 Hz,
CH3CH2OP), 3.58 (dd, 1H, JHP¼19.8 Hz, JHH¼11.7 Hz,
3JHH¼11.1 Hz, ArCHCHAHBNO2), 5.35 (dd, 1H, JHH
¼
PCHCOOH), 4.00–4.28 (m, 5H, 2ꢁCH3CH2OP, CHAr),
2
3
2
3
13.2 Hz, JHH¼4.2 Hz, ArCHCHAHBNO2), 7.39 (d, 2H,
4.88 (dd, 1H, JHH¼12.8 Hz, JHH¼11.7 Hz, ArCH-
3
2
3
3JHH¼8.5 Hz, 2ꢁCHAr), 7.50 (d, 2H, JHH¼8.5 Hz,
CHAHBNO2), 5.30 (dd, 1H, JHH¼12.8 Hz, JHH¼4.3 Hz,
2ꢁCHAr); 13C NMR (acetone-d): d¼16.55 (d, 3JCP¼3.5 Hz,
ArCHCHAHBNO2), 5.97 (s, 2H, CH2O2Ph), 6.75 (d, 1H,
3
3
CH3CH2OP), 16.64 (d, JCP¼3.3 Hz, CH3CH2OP), 43.43
3JHH¼8.0 Hz, CHAr), 6.85 (dd, 1H, JHH¼8.0 Hz,
2
1
4
(d, JCP¼3.9 Hz, ArCH), 49.32 (d, JCP¼126.3 Hz,
4JHH¼1.6 Hz, CHAr), 6.99 (d, 1H, JHH¼1.6 Hz, CHAr);
2
3
PCHCOOH), 63.94 (d, JCP¼6.0 Hz, CH3CH2OP), 64.04
13C NMR (acetone-d): d¼16.47 (d, JCP¼4.0 Hz,
2
3
(d, JCP¼6.5 Hz, CH3CH2OP), 79.31 (CH2NO2), 121.30
CH3CH2OP), 16.55 (d, JCP¼5.5 Hz, CH3CH2OP), 43.70
2
1
(CAr), 131.51 (CHAr), 132.39 (CHAr), 138.34 (d,
3JCP¼15.7 Hz, CAr), 168.32 (d, 2JCP¼5.6 Hz, PCHCOOH).
Anal. calcd for C14H19BrNO7P: C, 39.64; H, 4.51; N, 3.30.
Found: C, 39.51; H, 4.39; N, 3.40.
(d, JCP¼3.9 Hz, ArCH), 49.63 (d, JCP¼126.0 Hz,
2
PCHCOOH), 64.05 (d, JCP¼6.6 Hz, 2ꢁCH3CH2OP),
79.61 (CH2NO2), 102.13 (CH2O2Ph), 108.77 (CHAr),
109.13 (CHAr), 123.08 (CHAr), 132.19 (d, JCP¼16.4 Hz,
3
2
CAr), 148.14 (CAr), 148.56 (CAr), 168.34 (d, JCP¼5.7 Hz,
4.4.3. (2R*,3R*)-2-(Diethoxyphosphoryl)-3-(4-methyl-
phenyl)-4-nitrobutanoic acid (5c). 799 mg, 89% yield,
white crystals, mp 112–115 ꢂC; IR (CCl4): 1736, 1552,
PCHCOOH). Anal. calcd for C15H20NO9P: C, 46.28; H,
5.18; N, 3.60. Found: C, 46.41; H, 5.33; N, 3.72.
1220, 1040, 1016 cmꢀ1
;
31P NMR (acetone-d): d¼20.16;
4.4.6. (2R*,3R*,4R*)-2-(Diethoxyphosphoryl)-4-nitro-3-
(4-nitrophenyl)pentanoic acid (6a). 859 mg, 85% yield,
white crystals, mp 155–157 ꢂC; IR (CCl4): 1728, 1528,
3
1H NMR (acetone-d): d¼1.34 (t, 3H, JHH¼7.1 Hz,
3
CH3CH2OP), 1.35 (t, 3H, JHH¼7.1 Hz, CH3CH2OP), 2.26
(s, 3H, CH3Ph), 3.60 (dd, 1H, 2JHP¼19.8 Hz, 3JHH¼11.8 Hz,
1352, 1232, 1160, 1024, 664 cmꢀ1 31P NMR (acetone-d):
;
PCHCOOH), 4.03–4.26 (m, 5H, 2ꢁCH3CH2OP, CHAr),
d¼19.42; 1H NMR (acetone-d):d¼1.35 (t, 3H, 3JHH¼7.1 Hz,
2
3
3
4.89 (dd, 1H, JHH¼13.0 Hz, JHH¼11.2 Hz, ArCH-
CH3CH2OP), 1.35 (t, 3H, JHH¼7.1 Hz, CH3CH2OP), 1.47
2
3
3
CHAHBNO2), 5.32 (dd, 1H, JHH¼13.0 Hz, JHH¼4.2 Hz,
(d, 3H, JHH¼6.7 Hz, CH3CHNO2), 3.88 (dd, 1H,
3
3
ArCHCHAHBNO2), 7.10 (d, 2H, JHH¼7.5 Hz, 2ꢁCHAr),
2JHP¼21.0 Hz, JHH¼12.0 Hz, PCHCOOH), 4.17–4.29 (m,
7.28 (d, 2H, JHH¼7.5 Hz, 2ꢁCHAr); 13C NMR (acetone-
4H, 2ꢁCH3CH2OP), 4.47 (ddd, 1H, JHH¼12.0, JHP¼
3
3
3
3
d): d¼16.41 (d, JCP¼4.1 Hz, CH3CH2OP), 16.50 (d,
8.2 Hz, 3JHH¼4.3 Hz, Ar–CH), 5.53 (dq, 1H, 3JHH¼6.7 Hz,
3JCP¼4.1 Hz, CH3CH2OP), 20.96 (CH3Ph), 43.34 (d,
3JHH¼4.3 Hz, CH3CHNO2), 7.57 (d, 2H, JHH¼8.8 Hz,
3
2JCP¼4.2 Hz, ArCH), 49.45 (d, 1JCP¼126.9 Hz,
2ꢁCHAr), 8.21 (d, 2H, JHH¼8.8 Hz, 2ꢁCHAr); 13C NMR
3
2
PCHCOOH), 64.09 (CH3CH2OP), 64.19 (d, JCP¼1.7 Hz,
(acetone-d): d¼12.96 (CH3CHNO2), 16.47 (d, 3JCP¼3.4 Hz,
CH3CH2OP), 16.56 (d, 3JCP¼3.3 Hz, CH3CH2OP), 47.79 (d,
CH3CH2OP), 79.53 (CH2NO2), 128.99 (CHAr), 129.85
(CHAr), 135.44 (d, JCP¼16.0 Hz, CAr), 138.20 (CAr),
1JCP¼127.9 Hz, PCHCOOH), 48.39 (d, JCP¼3.1 Hz,
3
2
2
2
168.32 (d, JCP¼5.5 Hz, PCHCOOH). Anal. calcd for
ArCH), 64.02 (d, JCP¼2.7 Hz, CH3CH2OP), 64.14
C15H22NO7P: C, 50.14; H, 6.17; N, 3.90. Found: C, 50.25;
H, 6.29; N, 3.77.
(CH3CH2OP), 84.35 (CH3CHNO2), 123.96 (CHAr), 131.48
(CHAr), 143.74 (d, JCP¼16.0 Hz, CAr), 148.68 (CAr),
3
2
168.36 (d, JCP¼6.0 Hz, PCHCOOH). Anal. calcd for
4.4.4. (2R*,3R*)-2-(Diethoxyphosphoryl)-3-(4-methoxy-
phenyl)-4-nitrobutanoic acid (5d). 722 mg, 77% yield,
white crystals, mp 108–110 ꢂC; IR (CCl4): 1716, 1552,
C15H21N2O9P: C, 44.56; H, 5.24; N, 6.93. Found: C, 44.64;
H, 5.32; N, 6.80.
1256, 1172, 1028 cmꢀ1
;
31P NMR (acetone-d): d¼20.17;
4.4.7. (2R*,3R*,4R*)-3-(4-Bromophenyl)-2-(diethoxy-
phosphoryl)-4-nitropentanoic acid (6b). 975 mg, 89%
yield, white crystals, mp 156–158 ꢂC; IR (CCl4): 1736,
3
1H NMR (acetone-d): d¼1.34 (t, 3H, JHH¼7.0 Hz,
3
CH3CH2OP), 1.35 (t, 3H, JHH¼7.2 Hz, CH3CH2OP),
2
3
3.58 (dd, 1H, JHP¼19.8 Hz, JHH¼11.8 Hz, PCHCOOH),
3.76 (s, 3H, CH3OPh), 4.01–4.28 (m, 5H, 2ꢁCH3CH2OP,
CHAr), 4.88 (dd, 1H, 2JHH¼12.8 Hz, 3JHH¼11.2 Hz, ArCH-
1552, 1224, 1164, 1024, 664 cmꢀ1 31P NMR (acetone-d):
;
d¼19.86; 1H NMR (acetone-d):d¼1.35 (t, 3H, 3JHH¼6.8 Hz,
3
CH3CH2OP), 1.36 (t, 3H, JHH¼7.0 Hz, CH3CH2OP),
2
3
3
CHAHBNO2), 5.30 (dd, 1H, JHH¼12.8 Hz, JHH¼4.5 Hz,
1.45 (d, 3H, JHH¼6.8 Hz, CH3CHNO2), 3.77 (dd,
3
ArCHCHAHBNO2), 6.84 (d, 2H, JHH¼8.5 Hz, 2ꢁCHAr),
1H, 2JHP¼20.5 Hz, 3JHH¼12.2 Hz, PCHCOOH), 4.17–4.29
7.32 (d, 2H, 3JHH¼8.5 Hz, 2ꢁCHAr); 13C NMR (acetone-d):
(m, 4H, 2ꢁCH3CH2OP), 4.34 (ddd, 1H, JHH¼12.2,
3

9142
H. Krawczyk et al. / Tetrahedron 62 (2006) 9135–9145
3
3
3
3JHP¼8.2 Hz, JHH¼4.2 Hz, Ar–CH), 5.45 (dq, 1H, JHH
¼
¼
3JHH¼7.0 Hz, CH3CH2OP), 1.36 (t, 3H, JHH¼7.0 Hz,
3
3
3
6.8 Hz, JHH¼4.2 Hz, CH3CHNO2), 7.19 (d, 2H, JHH
CH3CH2OP), 1.46 (d, 3H, JHH¼6.6 Hz, CH3CHNO2),
3
2
3
8.5 Hz, 2ꢁCHAr), 7.50 (d, 2H, JHH¼8.5 Hz, 2ꢁCHAr);
3.68 (dd, 1H, JHP¼20.4 Hz, JHH¼12.2 Hz, PCHCOOH),
13C NMR (acetone-d): d¼12.66 (CH3CHNO2), 16.44 (d,
4.17–4.29 (m, 4H, 2ꢁCH3CH2OP), 4.29 (ddd, 1H,
3JCP¼3.0 Hz, CH3CH2OP), 16.54 (d, JCP¼2.9 Hz,
3JHH¼12.2 Hz, JHP¼8.6 Hz, JHH¼4.2 Hz, Ar–CH), 5.40
3
3
3
CH3CH2OP), 47.82 (d, 1JCP¼127.9 Hz, PCHCOOH), 48.07
(d, 2JCP¼3.6 Hz, ArCH), 63.97 (d, 2JCP¼7.2 Hz,
CH3CH2OP), 64.08 (d, 2JCP¼6.5 Hz, CH3CH2OP), 84.32 (d,
3JCP¼1.7 Hz, CH3CHNO2), 122.53 (CAr), 132.05 (CHAr),
(dq, 1H, JHH¼6.6 Hz, JHH¼4.2 Hz, CH3CHNO2), 5.97
3
3
3
(s, 2H, CH2O2Ph), 6.65 (dd, 1H, JHH¼8.1 Hz,
4JHH¼1.6 Hz, CHAr), 6.75 (d, 1H, JHH¼8.1 Hz, CHAr),
3
6.76 (d, 1H, JHH¼1.6 Hz, CHAr); 13C NMR (acetone-d):
4
3
132.08 (CHAr), 135.30 (d, JCP¼16.4 Hz, CAr), 168.39 (d,
d¼12.64 (CH3CHNO2), 16.50 (2ꢁCH3CH2OP), 48.24 (d,
1JCP¼125.8 Hz, PCHCOOH), 48.31 (ArCH), 63.96
(2ꢁCH3CH2OP), 84.62 (CH3CHNO2), 102.12 (CH2O2Ph),
108.59 (CHAr), 110.06 (CHAr), 123.68 (CHAr), 129.34 (d,
3JCP¼17.2 Hz, CAr), 148.28 (CAr), 156.54 (CAr), 168.44
(PCHCOOH). Anal. calcd for C16H22NO9P: C, 47.65; H,
5.50; N, 3.47. Found: C, 47.77; H, 5.42; N, 3.56.
2JCP¼6.0 Hz, PCHCOOH). Anal. calcd for C15H21BrNO7P:
C, 41.11; H, 4.83; N, 3.20. Found: C, 41.23; H, 4.96; N, 3.30.
4.4.8. (2R*,3R*,4R*)-2-(Diethoxyphosphoryl)-3-(4-methyl-
phenyl)-4-nitropentanoic acid (6c). 783 mg, 84% yield,
white crystals, mp 148–150 ꢂC; IR (CCl4): 1720, 1552,
1164, 1020, 664 cmꢀ1
;
31P NMR (acetone-d): d¼20.36;
1H NMR (acetone-d): d¼1.36 (t, 3H, JHH¼7.0 Hz,
4.5. General procedure for the preparation of 4-aryl-3-
(diethoxyphosphoryl)-1-hydroxysuccinimides 8a–e
3
3
CH3CH2OP), 1.37 (t, 3H, JHH¼7.0 Hz, CH3CH2OP), 1.42
3
(d, 3H, JHH¼6.6 Hz, CH3CHNO2), 2.27 (s, 3H, CH3Ph),
2
3
3.72 (dd, 1H, JHP¼20.2 Hz, JHH¼12.3 Hz, PCHCOOH),
A solution of a corresponding 4-nitrobutanoic acid 5
(1 mmol) in water (15 mL) was heated at reflux for an appro-
priate period of time (shown in Table 2). The resulting solu-
tion was cooled to room temperature, the solvent was
evaporated and the residue was taken up in Et2O (10 mL)
and left to crystallize. Filtration of the crystals afforded
pure 1-hydroxysuccinimides 8.
4.18–4.28 (m, 4H, 2ꢁCH3CH2OP), 4.34 (ddd, 1H,
3JHH¼12.3 Hz, JHP¼8.4 Hz, JHH¼3.9 Hz, CHAr), 5.41
3
3
3
3
(dq, 1H, JHH¼6.6 Hz, JHH¼3.9 Hz, CH3CHNO2), 7.06
(s, 4H, 4ꢁCHAr); 13C NMR (acetone-d): d¼12.52
3
(CH3CHNO2), 16.45 (d, JCP¼3.3 Hz, CH3CH2OP), 16.55
3
(d, JCP¼3.2 Hz, CH3CH2OP), 20.95 (CH3Ph), 48.09 (d,
1JCP¼127.4 Hz, PCHCOOH), 48.20 (d, JCP¼3.8 Hz,
2
2
ArCH), 63.90 (d, JCP¼6.9 Hz, CH3CH2OP), 64.05 (d,
4.5.1. (3R*,4S*)-3-(Diethoxyphosphoryl)-4-(4-nitro-
phenyl)-1-hydroxysuccinimide (8a). 223 mg, 60% yield,
pale yellow crystals, mp 167–170 ꢂC; IR (CCl4): 1732,
2JCP¼6.4 Hz, CH3CH2OP), 84.54 (CH3CHNO2), 129.59
3
(CHAr), 129.90 (CHAr), 132.71 (d, JCP¼16.4 Hz, CAr),
2
138.43 (CAr), 168.51 (d, JCP¼6.0 Hz, PCHCOOH). Anal.
1528, 1348, 1208, 1032 cmꢀ1 31P NMR (acetone-d):
;
calcd for C16H24NO7P: C, 51.47; H, 6.48; N, 3.75. Found:
C, 51.59; H, 6.70; N, 3.67.
d¼18.97; 1H NMR (acetone-d): d¼1.26 (t, 3H,
3
3JHH¼7.0 Hz, CH3CH2OP), 1.30 (t, 3H, JHH¼7.0 Hz,
2
3
CH3CH2OP), 3.78 (dd, 1H, JHP¼23.0 Hz, JHH¼5.2 Hz,
4.4.9. (2R*,3R*,4R*)-2-(Diethoxyphosphoryl)-3-(4-meth-
oxyphenyl)-4-nitropentanoic acid (6d). 892 mg, 92%
yield, white crystals, mp 160–162 ꢂC; IR (CCl4): 1728,
PCHC(O)N), 4.07–4.28 (m, 4H, 2ꢁCH3CH2OP), 4.50 (dd,
3
3
1H, JHP¼18.0 Hz, JHH¼5.2 Hz, ArCHC(O)N), 7.77 (d,
3
3
2H, JHH¼8.8 Hz, 2ꢁCHAr), 8.28 (d, 2H, JHH¼8.8 Hz,
2ꢁCHAr); 13C NMR (acetone-d): d¼16.00 (d, 3JCP¼5.8 Hz,
CH3CH2OP), 16.09 (d, 3JCP¼5.7 Hz, CH3CH2OP), 44.86 (d,
1548, 1512, 1264, 1176, 1008, 960 cmꢀ1 31P NMR (ace-
;
tone-d): d¼20.61; 1H NMR (acetone-d): d¼1.35 (t, 3H,
3JHH¼7.0 Hz, CH3CH2OP), 1.36 (t, 3H, JHH¼7.2 Hz,
1JCP¼143.5 Hz, PCHC(O)N), 45.50 (d, JCP¼2.5 Hz,
3
2
3
2
CH3CH2OP), 1.43 (d, 3H, JHH¼6.8 Hz, CH3CHNO2),
ArCHC(O)N), 63.43 (d, JCP¼6.7 Hz, CH3CH2OP), 64.21
2
3
2
3.70 (dd, 1H, JHP¼20.2 Hz, JHH¼10.0 Hz, PCHCOOH),
3.76 (s, 3H, CH3OPh), 4.17–4.28 (m, 4H, 2ꢁCH3CH2OP),
(d, JCP¼6.4 Hz, CH3CH2OP), 124.14 (CHAr), 130.31
3
(CHAr), 143.83 (d, JCP¼3.0 Hz, CAr), 148.14 (CAr),
3
3
3
2
3
4.32 (ddd, 1H, JHH¼12.5 Hz, JHP¼8.2 Hz, JHH¼4.0 Hz,
166.49 (d, JCP¼4.4 Hz, C(O)NOH), 170.31 (d, JCP¼
3
3
CHAr), 5.39 (dq, 1H, JHH¼6.8 Hz, JHH¼4.0 Hz,
8.4 Hz, C(O)NOH). Anal. calcd for C14H17N2O8P: C,
45.17; H, 4.60; N, 7.53. Found: C, 45.30; H, 4.72; N, 7.41.
3
CH3CHNO2), 6.84 (d, 2H, JHH¼8.8 Hz, 2ꢁCHAr), 7.12
(d, 2H, 3JHH¼8.8 Hz, 2ꢁCHAr); 13C NMR (acetone-d): d¼
3
12.59 (CH3CHNO2), 16.54 (d, JCP¼3.3 Hz, CH3CH2OP),
4.5.2. (3R*,4S*)-4-(4-Bromophenyl)-3-(diethoxyphos-
phoryl)-1-hydroxysuccinimide (8b). 272 mg, 67% yield,
pale yellow crystals, mp 149–152 ꢂC; IR (CCl4): 1740,
3
2
16.63 (d, JCP¼3.2 Hz, CH3CH2OP), 47.98 (d, JCP
¼
1
3.6 Hz, ArCH), 48.32 (d, JCP¼127.0 Hz, PCHCOOH),
2
55.46 (CH3OPh), 63.81 (d, JCP¼6.3 Hz, CH3CH2OP),
1220, 1036 cmꢀ1
;
31P NMR (acetone-d): d¼19.24; 1H
2
3
4
63.89 (d, JCP¼4.7 Hz, CH3CH2OP), 84.72 (CH3CHNO2),
NMR (acetone-d): d¼1.26 (dt, 3H, JHH¼7.1 Hz, JHP
¼
3
3
4
114.34 (CHAr), 127.87 (d, JCP¼18.2 Hz, CAr), 131.19
0.4 Hz, CH3CH2OP), 1.30 (dt, 3H, JHH¼7.0 Hz, JHP
¼
(CHAr), 160.40 (CAr), 168.57 (d, 2JCP¼5.9 Hz, PCHCOOH).
Anal. calcd for C16H24NO8P: C, 49.36; H, 6.21; N, 3.60.
Found: C, 49.49; H, 6.33; N, 3.67.
0.5 Hz, CH3CH2OP), 3.63 (dd, 1H, JHP¼23.1 Hz,
2
3JHH¼4.8 Hz,
PCHC(O)N),
4.05–4.26
(m,
4H,
2ꢁCH3CH2OP), 4.27 (dd, 1H, 3JHP¼18.1 Hz, 3JHH¼4.8 Hz,
ArCHC(O)N), 7.39 (d, 2H, 3JHH¼7.5 Hz, 2ꢁCHAr), 7.59 (d,
3
4.4.10. (2R*,3R*,4R*)-2-(Diethoxyphosphoryl)-3-(3,4-
methylenedioxyphenyl)-4-nitropentanoic acid (6e).
937 mg, 93% yield, white crystals, mp 163–166 ꢂC; IR
2H, JHH¼7.5 Hz, 2ꢁCHAr); 13C NMR (acetone-d): d¼
16.45 (d, 3JCP¼5.9 Hz, CH3CH2OP), 16.54 (d, 3JCP¼5.7 Hz,
CH3CH2OP), 45.53 (d, 1JCP¼142.8 Hz, PCHC(O)N), 45.73
(ArCHC(O)N), 63.87 (d, 2JCP¼6.6 Hz, CH3CH2OP), 64.64
(CCl4): 1736, 1552, 1224, 1040, 664 cmꢀ1 31P NMR (ace-
;
tone-d): d¼20.08; 1H NMR (acetone-d): d¼1.35 (t, 3H,
(d, JCP¼6.4 Hz, CH3CH2OP), 122.44 (CAr), 131.30
2

H. Krawczyk et al. / Tetrahedron 62 (2006) 9135–9145
9143
3
(CHAr), 132.70 (CHAr), 136.55 (d, JCP¼3.5 Hz, CAr),
4.6. General procedure for the preparation of dicyclo-
hexylammonium 3-aryl-2-(diethoxyphosphoryl)-4-oxo-
pentanoates 10a–e
3
167.09 (C(O)NOH), 171.27 (d, JCP¼8.4 Hz, C(O)NOH).
Anal. calcd for C14H17BrNO6P: C, 41.40; H, 4.22; N, 3.45.
Found: C, 41.51; H, 4.31; N, 3.30.
A solution of 4-nitropentanoic acid 6 (1 mmol) in water
(15 mL) was heated at reflux for an appropriate period of
time (shown in Table 2). The resulting solution was cooled
to room temperature and the solvent was evaporated. The
residue was dissolved in CH2Cl2 (10 mL) and dicyclohexyl-
amine (1 mmol, 181 mg) was added. The solvent was evapo-
rated off and the residue was taken up in Et2O (10 mL)
and left to crystallize. Filtration of the crystals afforded
pure 4-oxopentanoates 10.
4.5.3. (3R*,4S*)-3-(Diethoxyphosphoryl)-4-(4-methyl-
phenyl)-1-hydroxysuccinimide (8c). 232 mg, 68% yield,
pale yellow crystals, mp 158–161 ꢂC; IR (CCl4): 1720,
1512, 1356, 1216, 1032 cmꢀ1 31P NMR (acetone-d):
;
d¼18.97; 1H NMR (CDCl3): d¼1.31–141 (m, 6H,
2ꢁCH3CH2OP), 2.35 (s, 3H, CH3Ph), 3.51 (dd, 1H,
3
2JHP¼24.5 Hz, JHH¼4.5 Hz, PCHC(O)N), 4.11–4.33 (m,
3
5H, 2ꢁCH3CH2OP, ArCHC(O)N), 7.08 (d, 2H, JHH
¼
3
8.0 Hz, 2ꢁCHAr), 7.20 (d, 2H, JHH¼8.0 Hz, 2ꢁCHAr);
13C NMR (CH3OD): d¼15.63 (d, 3JCP¼4.9 Hz,
4.6.1. Dicyclohexylammonium (2R*,3S*)-2-(diethoxy-
phosphoryl)-3-(4-nitrophenyl)-4-oxopentanoate (10a).
388 mg, 70% yield, pale yellow crystals, mp 163–165 ꢂC;
IR (CCl4): 2936, 1712, 1512, 1344, 1240, 1056, 1032,
3
CH3CH2OP), 15.71 (d, JCP¼5.3 Hz, CH3CH2OP), 20.25
1
(CH3Ph), 45.40 (d, JCP¼142.3 Hz, PCHC(O)N), 45.60 (d,
2JCP¼2.4 Hz, ArCHC(O)N), 63.95 (d, JCP¼6.7 Hz,
2
2
CH3CH2OP), 64.50 (d, JCP¼6.6 Hz, CH3CH2OP), 128.02
968 cmꢀ1
;
31P NMR (CDCl3): d¼25.56; 1H NMR
3
3
(CHAr), 129.87 (CHAr), 133.22 (d, JCP¼3.8 Hz, CAr),
(CDCl3): d¼0.97 (t, 3H, JHH¼7.1 Hz, CH3CH2OP), 1.11
2
3
138.52 (CAr), 167.44 (d, JCP¼4.4 Hz, C(O)NOH),
(t, 3H, JHH¼7.1 Hz, CH3CH2OP), 1.16–1.38 (m, 6H, 3ꢁ
3
172.23 (d, JCP¼7.5 Hz, C(O)NOH). Anal. calcd for
CH2(cHex)), 1.40–1.90 (m, 10H, 5ꢁCH2(cHex)), 1.98–
C15H20NO6P: C, 52.79; H, 5.91; N, 4.10. Found: C, 52.71;
H, 6.03; N, 3.97.
2.35 (m, 4H, 2ꢁCH2(cHex)), 2.13 (s, 3H, CH3CO), 2.98–
2
3.07 (m, 2H, 2ꢁCH(cHex)), 3.65 (dd, 1H, JHP¼20.6 Hz,
3JHH¼11.8 Hz, PCHCOOꢀ), 3.67–4.12 (m, 4H,
4.5.4. (3R*,4S*)-3-(Diethoxyphosphoryl)-4-(4-methoxy-
phenyl)-1-hydroxysuccinimide (8d). 228 mg, 64% yield,
pale yellow crystals, mp 174–175 ꢂC; IR (CCl4): 1728,
2ꢁCH3CH2OP), 4.70 (dd, 1H, 3JHH¼11.8 Hz, 3JHP¼8.5 Hz,
3
ArCH), 7.54 (d, 2H, JHH¼8.7 Hz, 2ꢁCHAr), 8.16 (d, 2H,
3JHH¼8.7 Hz, 2ꢁCHAr); 13C NMR (CDCl3): d¼15.66
3
3
1516, 1256, 1216, 1040 cmꢀ1
;
31P NMR (acetone-d):
(d, JCP¼6.7 Hz, CH3CH2OP), 15.78 (d, JCP¼7.9 Hz,
3
d¼19.48; 1H NMR (acetone-d): d¼1.26 (dt, 3H, JHH
¼
CH3CH2OP), 24.56 (CH2(cHex)), 24.80 (CH2(cHex)),
¼
1
7.2 Hz, 4JHP¼0.5 Hz, CH3CH2OP), 1.30 (dt, 3H,
28.50 (CH2(cHex)), 29.34 (CH3CO), 51.68 (d, JCP
126.0 Hz, PCHCOOꢀ), 52.21 (ArCH), 57.48 (CH(cHex)),
4
3JHH¼7.0 Hz, JHP¼0.5 Hz, CH3CH2OP), 3.54 (dd, 1H,
2JHP¼23.2 Hz, JHH¼4.5 Hz, PCHC(O)N), 3.80 (s, 3H,
60.76 (d, 2JCP¼6.8 Hz, CH3CH2OP), 61.85 (d, 2JCP¼6.2 Hz,
3
CH3OPh), 4.08–4.25 (m, 5H, 2ꢁCH3CH2OP, ArCHC(O)N),
CH3CH2OP), 123.08 (CHAr), 130.02 (CHAr), 143.80 (CAr),
¼
3
3
6.94 (d, 2H, JHH¼9.0 Hz, 2ꢁCHAr), 7.30 (d, 2H,
146.87 (CAr), 170.10 (PCHCOOꢀ), 205.08 (d, JCP
3JHH¼9.0 Hz, 2ꢁCHAr); 13C NMR (acetone-d): d¼16.79
18.2 Hz, CH3CO). Anal. calcd for C27H43N2O8P: C, 58.47;
H, 7.81; N, 5.05. Found: C, 58.61; H, 7.73; N, 5.15.
3
3
(d, JCP¼5.6 Hz, CH3CH2OP), 16.88 (d, JCP¼5.3 Hz,
1
CH3CH2OP), 45.98 (ArCHC(O)N), 46.33 (d, JCP
141.5 Hz, PCHC(O)N), 55.90 (CH3OPh), 64.13 (d, JCP
¼
¼
2
4.6.2. Dicyclohexylammonium (2R*,3S*)-3-(4-bromo-
phenyl)-2-(diethoxyphosphoryl)-4-oxopentanoate (10b).
329 mg, 56% yield, white crystals, mp 155–157 ꢂC; IR
(CCl4): 2936, 1712, 1636, 1356, 1240, 1056, 1032,
2
6.7 Hz, CH3CH2OP), 64.86 (d, JCP¼6.4 Hz, CH3CH2OP),
115.40 (CHAr), 129.50 (CAr), 130.48 (CHAr), 160.74 (CAr),
2
3
167.64 (d, JCP¼4.7 Hz, C(O)NOH), 172.17 (d, JCP
¼
7.4 Hz, C(O)NOH). Anal. calcd for C15H20NO7P: C,
50.42; H, 5.64; N, 3.92. Found: C, 50.51; H, 5.75;
N, 3.82.
968 cmꢀ1
;
31P NMR (CDCl3): d¼26.04; 1H NMR
3
(CDCl3): d¼0.97 (t, 3H, JHH¼7.0 Hz, CH3CH2OP), 1.12
3
(t, 3H, JHH¼7.0 Hz, CH3CH2OP), 1.18–1.34 (m, 6H,
3ꢁCH2(cHex)), 1.39–1.58 (m, 4H, 2ꢁCH2(cHex)),
1.60–1.70 (m, 2H, CH2(cHex)), 1.74–1.88 (m, 4H,
2ꢁCH2(cHex)), 1.95–2.07 (m, 4H, 2ꢁCH2(cHex)), 2.08 (s,
3H, CH3CO), 2.94–3.04 (m, 2H, 2ꢁCH(cHex)), 3.57 (dd,
4.5.5. (3R*,4S*)-3-(Diethoxyphosphoryl)-4-(3,4-methyl-
enedioxyphenyl)-1-hydroxysuccinimide (8e). 293 mg, 79%
yield, pale yellow crystals, mp 210–211 ꢂC; IR (CCl4):
2
3
1724, 1504, 1256, 1220, 1032 cmꢀ1
;
31P NMR (acetone-d):
1H, JHP¼20.6 Hz, JHH¼11.8 Hz, PCHCOOꢀ), 3.59–4.11
3
d¼19.42; 1H NMR (acetone-d): d¼1.26 (t, 3H, 3JHH¼7.0 Hz,
(m, 4H, 2ꢁCH3CH2OP), 4.53 (dd, 1H, JHH¼11.8 Hz,
3
CH3CH2OP), 1.30 (t, 3H, JHH¼7.0 Hz, CH3CH2OP), 3.55
3JHP¼8.6 Hz, ArCH), 7.22 (d, 2H, 3JHH¼8.5 Hz, 2ꢁCHAr),
2
3
3
(dd, 1H, JHP¼23.0 Hz, JHH¼4.8 Hz, PCHC(O)N), 4.06–
4.26 (m, 5H, 2ꢁCH3CH2OP, ArCHC(O)N), 6.02 (s,
7.41 (d, 2H, JHH¼8.5 Hz, 2ꢁCHAr); 13C NMR (CDCl3):
3
3
d¼15.70 (d, JCP¼7.3 Hz, CH3CH2OP), 15.82 (d, JCP
¼
2H, CH2O2Ph), 6.83–6.93 (m, 3H, 3ꢁCHAr); 13C NMR
7.7 Hz, CH3CH2OP), 24.66 (CH2(cHex)), 24.91
(CH2(cHex)), 28.59 (CH2(cHex)), 29.02 (CH3CO), 51.53
1
(acetone-d): d¼16.55 (2ꢁCH3CH2OP), 46.04 (d, JCP
¼
1
143.2 Hz, PCHC(O)N), 46.12 (ArCHC(O)N), 63.75
(CH3CH2OP), 64.86 (CH3CH2OP), 102.16 (CH2O2Ph),
109.08 (CHAr), 109.69 (CHAr), 122.77 (CHAr), 123.46
(d, JCP¼127.4 Hz, PCHCOOꢀ), 52.51 (ArCH), 57.24
2
(CH(cHex)), 60.63 (d, JCP¼6.6 Hz, CH3CH2OP), 61.80
2
(d, JCP¼6.6 Hz, CH3CH2OP), 121.04 (CAr), 130.96
2
2
(CAr), 130.87 (CAr), 148.42 (CAr), 167.25 (d, JCP¼5.9 Hz,
(CHAr), 131.17 (CHAr), 135.21 (CAr), 170.65 (d, JCP
¼
3
3
C(O)NOH), 171.57 (d, JCP¼6.9 Hz, C(O)NOH). Anal.
3.8 Hz, PCHCOOꢀ), 205.72 (d, JCP¼18.2 Hz, CH3CO).
Anal. calcd for C27H43BrNO6P: C, 55.10; H, 7.36; N, 2.38.
Found: C, 55.01; H, 7.23; N, 2.27.
calcd for C15H18NO8P: C, 48.52; H, 4.89; N, 3.77. Found:
C, 48.62; H, 5.00; N, 3.70.

9144
H. Krawczyk et al. / Tetrahedron 62 (2006) 9135–9145
4.6.3. Dicyclohexylammonium (2R*,3S*)-2-(diethoxy-
phosphoryl)-3-(4-methylphenyl)-4-oxopentanoate (10c).
261 mg, 50% yield, white crystals, mp 122–124 ꢂC; IR
(CCl4): 2936, 1720, 1512, 1356, 1248, 1032, 968,
2ꢁCH2(cHex)), 1.95–2.06 (m, 4H, 2ꢁCH2(cHex)), 2.08 (s,
3H, CH3CO), 2.87–3.02 (m, 2H, 2ꢁCH(cHex)), 3.55 (dd,
2
3
1H, JHP¼20.6 Hz, JHH¼11.7 Hz, PCHCOOꢀ), 3.64–4.13
3
(m, 4H, 2ꢁCH3CH2OP), 4.47 (dd, 1H, JHH¼11.7 Hz,
664 cmꢀ1
;
31P NMR (CDCl3): d¼26.33; 1H NMR
3JHP¼8.8 Hz, ArCH), 5.91 (s, 2H, CH2OPh), 6.73 (d, 1H,
3
(CDCl3): d¼0.96 (t, 3H, JHH¼7.1 Hz, CH3CH2OP), 1.10
3JHH¼8.0 Hz, CHAr), 6.81 (s, 1H, CHAr), 6.83 (d, 1H, 3JHH
¼
¼
3
3
(t, 3H, JHH¼7.0 Hz, CH3CH2OP), 1.19–1.35 (m, 6H,
8.0 Hz, CHAr); 13C NMR (CDCl3): d¼15.61 (d, JCP
3
3ꢁCH2(cHex)), 1.41–1.68 (m, 6H, 3ꢁCH2(cHex)), 1.76–
1.86 (m, 4H, 2ꢁCH2(cHex)), 1.98–2.03 (m, 4H,
2ꢁCH2(cHex)), 2.06 (s, 3H, CH3CO), 2.30 (s, 3H, CH3Ph),
2.95–3.04 (m, 2H, 2ꢁCH(cHex)), 3.62 (dd, 1H,
3.6 Hz, CH3CH2OP), 15.71 (d, JCP¼4.0 Hz, CH3CH2OP),
24.51 (CH2(cHex)), 24.75 (CH2(cHex)), 28.44 (CH2(cHex)),
1
28.62 (CH3CO), 51.39 (d, JCP¼127.2 Hz, PCHCOOꢀ),
2
52.01 (ArCH), 57.21 (CH(cHex)), 60.44 (d, JCP¼6.5 Hz,
3
2
2JHP¼20.8 Hz, JHH¼11.3 Hz, PCHCOOꢀ), 3.55–4.11 (m,
CH3CH2OP), 61.50 (d, JCP¼6.5 Hz, CH3CH2OP), 100.52
3
4H, 2ꢁCH3CH2OP), 4.50 (dd, 1H, JHH¼11.3 Hz,
(CH2O2Ph), 107.70 (CHAr), 109.12 (CHAr), 122.72 (CHAr),
129.57 (CAr), 146.45 (CAr), 147.15 (CAr), 170.75 (d,
3JHP¼9.1 Hz, ArCH), 7.08 (d, 2H, 3JHH¼7.5 Hz, 2ꢁCHAr),
3
3
7.22 (d, 2H, JHH¼7.5 Hz, 2ꢁCHAr); 13C NMR (CDCl3):
2JCP¼3.8 Hz, PCHCOOꢀ), 205.85 (d, JCP¼19.6 Hz,
3
3
d¼15.60 (d, JCP¼6.6 Hz, CH3CH2OP), 15.75 (d, JCP
¼
CH3CO). Anal. calcd for C28H44NO8P: C, 60.75; H, 8.01;
N, 2.53. Found: C, 60.87; H, 8.13; N, 2.45.
7.1 Hz, CH3CH2OP), 20.71 (CH3Ph), 24.62 (CH2(cHex)),
24.84 (CH2(cHex)), 28.56 (CH2(cHex)), 28.78 (CH3CO),
51.40 (d, JCP¼127.2 Hz, PCHCOOꢀ), 52.19 (ArCH),
4.7. X-ray single crystal structure analysis for 8b
1
2
57.44 (CH(cHex)), 60.64 (d, JCP¼6.7 Hz, CH3CH2OP),
2
61.66 (d, JCP¼6.6 Hz, CH3CH2OP), 128.76 (CHAr),
Formula: C14H17NO6PBr, Mw¼406.20, pale yellow crystal
0.40ꢁ0.30ꢁ0.20 mm, a¼8.3309(4), b¼10.0423(4), c¼
129.10 (CHAr), 132.84 (CAr), 136.54 (CAr), 171.13 (d,
2JCP¼3.8 Hz, PCHCOOꢀ), 206.13 (d, JCP¼19.3 Hz,
11.7799(4) A, a¼74.941(4), b¼76.686(4), g¼65.860(4) ,
3
ꢂ
˚
3
V¼859.81(6) A , rcalc¼1.569 g cmꢀ3, m¼2.51 cmꢀ1, Z¼2,
˚
CH3CO). Anal. calcd for C28H46NO6P: C, 64.22; H, 8.85;
N, 2.67. Found: C, 64.34; H, 8.96; N, 2.77.
˚
crystal system: triclinic, space group: P-1, l¼0.71073 A,
T¼293 K, u scans, 8916 reflections collected (ꢃh,ꢃk,ꢃl),
2qmax¼50ꢂ, 2932 unique reflections (Rint¼0.021) and 2406
observed reflections [Iꢄ2s(I)], 239 refined parameters, re-
finement on F2, Rall¼0.059, wR(F2)¼0.145, max. and min.
4.6.4. Dicyclohexylammonium 2-(diethoxyphosphoryl)-
3-(4-methoxyphenyl)-4-oxopentanoate (10d). 333 mg,
62% yield, white crystals, mp 136–138 ꢂC; IR (CCl4):
2936, 1716, 1512, 1356, 1248, 1032 cmꢀ1
;
31P NMR
residual electron density (Drmax¼0.88 and Drmin¼
˚
(CDCl3): d¼26.30, 26.71 (81:19); (2R*,3S*)-10d: 31P
ꢀ0.85) eAꢀ3—both peaks located near Br atom, X-ray data
were collected with Kuma Diffraction KM4 CCD area detec-
tor diffractometer. Structure was solved by direct methods
and refined by full matrix least-squares—SHELXTL.26
1
NMR (CDCl3): d¼26.30; H NMR (CDCl3): d¼0.98 (t,
3
3
3H, JHH¼7.0 Hz, CH3CH2OP), 1.12 (t, 3H, JHH¼7.2 Hz,
CH3CH2OP), 1.18–1.34 (m, 6H, 3ꢁCH2(cHex)), 1.40–
1.67 (m, 6H, 3ꢁCH2(cHex)), 1.76–1.86 (m, 4H,
2ꢁCH2(cHex)), 1.97–2.04 (m, 4H, 2ꢁCH2(cHex)), 2.05
(s, 3H, CH3CO), 2.91–3.04 (m, 2H, 2ꢁCH(cHex)), 3.60
(dd, 1H, 2JHP¼20.8 Hz, 3JHH¼11.8 Hz, PCHCOOꢀ), 3.55–
4.20 (m, 4H, 2ꢁCH3CH2OP), 3.78 (s, 3H, CH3OPh), 4.49
(dd, 1H, 3JHH¼11.8 Hz, 3JHP¼8.8 Hz, ArCH), 6.82 (d, 2H,
Crystallographic data (excluding structure factors) for the
structure reported herein, have been deposited with the Cam-
bridge Crystallographic Data Centre as supplementary pub-
lication CCDC 605788. Copies of the data can be obtained
free of charge on application to The Director, CCDC, 12
Union Road, Cambridge CB2 1EZ, UK. Any request should
be accompanied by a full literature citation.
3
3JHH¼8.8 Hz, 2ꢁCHAr), 7.24 (d, 2H, JHH¼8.8 Hz,
3
2ꢁCHAr); 13C NMR (CDCl3): d¼15.75 (d, JCP¼5.5 Hz,
3
CH3CH2OP), 15.84 (d, JCP¼6.2 Hz, CH3CH2OP), 24.65
(CH2(cHex)), 24.88 (CH2(cHex)), 28.59 (CH2(cHex)),
1
28.76 (CH3CO), 51.48 (d, JCP¼127.3 Hz, PCHCOOꢀ),
Acknowledgements
52.17 (ArCH), 54.97 (CH3OPh), 57.01 (CH(cHex)), 60.61
(d, JCP¼6.7 Hz, CH3CH2OP), 61.56 (d, JCP¼7.5 Hz,
2
2
This work was financed by the Ministry of Education and Sci-
ence (Project No. 3 T09A 075 28, to H.K. and q.A.) and the
Institute of General and Ecological Chemistry (J.W. and
W.M.W.). q.A. is a grant holder of ‘Mechanizm WIDDOK’
program supported by European Social Fund and Polish State
(contract number Z/2.10/II/2.6/04/05/U/2/06).
CH3CH2OP), 113.57 (CHAr), 127.98 (CAr), 130.29 (CHAr),
2
158.36 (CAr), 171.12 (d, JCP¼3.8 Hz, PCHCOOꢀ),
3
206.17 (d, JCP¼19.2 Hz, CH3CO). Anal. calcd for
C28H46NO7P: C, 62.32; H, 8.59; N, 2.60. Found: C, 62.33;
H, 8.70; N, 2.47.
4.6.5. Dicyclohexylammonium 2-(diethoxyphosphoryl)-
3-(3,4-methylenedioxyphenyl)-4-oxopentanoate (10e).
326 mg, 59% yield, pale yellow crystals, mp 144–146 ꢂC;
IR (CCl4): 2936, 1712, 1612, 1484, 1352, 1240, 1040,
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;
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3
´
ꢀ
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