Novel 5-arylcarbamoyl-2-methylisoxazolidin-3-yl-3-phosphonates as nucleotide analogues

Article abstract of DOI:10.1080/15257770.2014.909046

A series of 5-substituted 3-phosphonylated isoxazolidines have been obtained via cycloaddition of N-methyl-C-(diethoxyphosphoryl)nitrone with N-heteroaromatic acrylamides. Good trans/cis diastereoselectivities (d.e. 58-76%) of isomeric (3-diethoxyphosphoryl)isoxazolidines were observed. cis-and trans-Isoxazolidine phosphonates were evaluated for their antiviral activity against a broad range of DNA and RNA viruses but were found inactive. Their cytostatic activity toward L1210, CEM, and HeLa cells was also established, and compounds cis-12r and trans-11r having a 2,2-difluorobenzo[d][1,3]dioxole moiety slightly inhibited proliferation of HeLa cells at IC50 values of 186 and 179 M, respectively.

Full text of DOI:10.1080/15257770.2014.909046

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Novel 5-Arylcarbamoyl-2-
methylisoxazolidin-3-yl-3-phosphonates
as Nucleotide Analogues
Kamil Kokoszaa, Jan Balzarinib & Dorota G. Piotrowskaa
a Bioorganic Chemistry Laboratory, Faculty of Pharmacy, Medical
University of Łódź, Łódź, Muszyńskiego, Poland
b Rega Institute for Medical Research, KU Leuven,
Minderbroedersstraat, Leuven, Belgium
Published online: 10 Jul 2014.
To cite this article: Kamil Kokosza, Jan Balzarini & Dorota G. Piotrowska (2014) Novel 5-
Arylcarbamoyl-2-methylisoxazolidin-3-yl-3-phosphonates as Nucleotide Analogues, Nucleosides,
Nucleotides and Nucleic Acids, 33:8, 552-582, DOI: 10.1080/15257770.2014.909046
To link to this article: http://dx.doi.org/10.1080/15257770.2014.909046
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Nucleosides, Nucleotides and Nucleic Acids, 33:552–582, 2014
Copyright ꢀC Taylor and Francis Group, LLC
ISSN: 1525-7770 print / 1532-2335 online
DOI: 10.1080/15257770.2014.909046
NOVEL 5-ARYLCARBAMOYL-2-METHYLISOXAZOLIDIN-3-YL-3-
PHOSPHONATES AS NUCLEOTIDE
ANALOGUES
Kamil Kokosza,1 Jan Balzarini,2 and Dorota G. Piotrowska1
1Bioorganic Chemistry Laboratory, Faculty of Pharmacy, Medical University of Ło´dz´, Ło´dz´,
Muszyn´skiego, Poland
2Rega Institute for Medical Research, KU Leuven, Minderbroedersstraat, Leuven, Belgium
A series of 5-substituted 3-phosphonylated isoxazolidines have been obtained via cycloaddition
2
of N-methyl-C-(diethoxyphosphoryl)nitrone with N-heteroaromatic acrylamides. Good trans/cis di-
astereoselectivities (d.e. 58–76%) of isomeric (3-diethoxyphosphoryl)isoxazolidines were observed.
cis- and trans-Isoxazolidine phosphonates were evaluated for their antiviral activity against a broad
range of DNA and RNA viruses but were found inactive. Their cytostatic activity toward L1210,
CEM, and HeLa cells was also established, and compounds cis-12r and trans-11r having a 2,2-
difluorobenzo[d][1,3]dioxole moiety slightly inhibited proliferation of HeLa cells at IC50 values of
186 and 179 μM, respectively.
Keywords Modified nucleosides; phosphonates; isoxazolidines; 1,3-dipolar cycloaddi-
tion
INTRODUCTION
Analogues of nucleosides constitute an important class of compounds
in contemporary medicinal chemistry. An extensive body of literature deals
with modified nucleosides exhibiting antiviral,[1–3] anticancer,[4–6] antibacte-
rial,[7–9] and antimalarial[10] activities. Structural modifications of naturally
occurring nucleosides to design potentially active nucleoside analogues pre-
dominantly concern sugar and nucleobase moieties. Moreover, a replace-
ment of the furanoside fragment is not limited to other alicyclic or hetero-
cyclic rings containing one or more heteroatoms, but aliphatic chains can
also be incorporated.[11–12] On the other hand, modifications of nucleobase
subunits to control a network of hydrogen bonds are not adequately ex-
plored. In order to improve the compounds’ biological activities, additional
Received 26 November 2013; accepted 21 March 2014.
Address correspondence to Bioorganic Chemistry Laboratory, Faculty of Pharmacy, Medical Uni-
versity of Ło´dz´, 90–151 Ło´dz´, Muszyn´skiego 1, Poland. E-mail: dorota.piotrowska@umed.lodz.pl
552

Novel 5-arylcarbamoyl-2-methylisoxazolidin-3-yl-3-phosphonates
553
FIGURE 1 Structures of nucleotide analogues approved for clinical use or subject of clinical trials.
linkers can be installed such as an ureidyl,[13] aminyl,[14] carbamoyl,[15–18] or
a 1,2,3-triazole group[19–22] to name a few.
In spite of a great number of nucleoside analogues available for treat-
ment of various types of cancers[23] and viral infections,[24] adverse effects,
low selectivity, and increasing resistance to currently used medications are
the main concerns in pharmacotherapy. The lack of activity of many obtained
nucleoside analogues results from their insufficient conversion to their cor-
responding triphosphates. Recently, more attention has been paid to phos-
phonate analogues of nucleotides since the rate-limiting step, namely, phos-
phorylation to the corresponding monophosphate could be omitted and
only two phosphorylation steps are required to reach their pharmacologi-
cally active form.[25] Extensive search in this field has led to the discovery of
many highly-active molecules that are licensed for clinical use, whereas others
are currently under clinical or preclinical investigation (Figure 1).[23,24,26–29]
Since 1992 when Tronchet proposed an isoxazolidine ring as an alter-
native to the furanose subunit,[30] many potent isoxazolidine nucleoside
analogues have been synthesized (Figure 2). Among them, compound 1
[(–)-AdFU] substituted at C5 with 5-fluorouracil-induced apoptosis in lym-
phoid and monocytoid cells and exhibits a low level of cytotoxicity.[31] Bor-
tolini et al. showed antiproliferative properties of 3,5-disubstituted isoxazo-
lidines 2.[32] Phosphonates of general formula 3, besides inhibiting reverse
transcriptase of HTLV-1 with activity comparable to that of AZT, protect hu-
man peripheral blood mononuclear cells against HTLV-1 transmission.[33]
Since N -methyl-C-(diethoxyphosphoryl)nitrone became available in suffi-
cient quantities,[34,35] a great deal of interest was generated due to its pos-
sible application in the synthesis of a novel class of nucleotides in which
the diethoxyphosphoryl group is directly attached to C3 of the isoxazolidine
ring. Biological studies showed that cis-configurated analogues containing

554
K. Kokosza et al.
FIGURE 2 Examples of biologically active isoxazolidine nucleosides and nucleotides.
thymine or 5-fluorouracil 4 inhibited the reverse transcriptase activity of two
retroviruses, namely, Avian Moloney Virus (AMV), and Human Immunode-
ficiency Virus (HIV).[36] At the same time, compounds 4 substituted with a
1- and 2-naphthyl proved cytostatic against HeLa and K562 cell lines at con-
centrations of 0.05 and 0.09 mM (IC50), respectively.[37] Recently, inhibitory
activity of derivatives 5 with an additional ethoxycarbonyl substituent against
HIV infection has also been reported.[38]
3,5-Disubstituted isoxazolidine analogues containing functionalized
1,2,3-triazoles 6 and a carbamoyl linker 7 have also been obtained. Although
none of them showed antiviral activity, cytostatic properties were discovered
for derivatives 6 substituted at C4 in the 1,2,3-triazole ring by phenyl, 2-fluoro,
3-fluoro-, and 2,4-difluorophenyl groups.[39] Recently, we have described
a convenient synthesis of 5-(arylcarbamoyl)isoxazolidine phosphonates 7,
and again derivatives having 2-fluorophenyl but also 3- and 4-bromophenyl
groups proved the most active toward three tested cancer cell lines.[40] In con-
tinuation of our search of antiviral and cytostatic properties of (isoxazolidine-
3-yl)phosphonates of general formula 8, it was assumed that the replace-
ment of aryl substituent acting as a nonpolar replacer of natural nucleobase
in 7 with various heteroaromatic rings could improve activity of the latter
molecules through formation of additional hydrogen bonds (Scheme 1).
The general concept of hydrogen-bonding patterns and shape complemen-
tarity of various heteroaromatic nucleobase isosters in order to study in-
teractions of nucleoside analogues with enzymes responsible for nucleic
acid synthesis were widely explored by several research groups.[41–44] Apart
from various nitrogen-containing heteroaromatic groups such as pyrazole,
pyridine, pyrimidine, pyrazine, benzo[d]imidazole, and indole, applied as
nucleobase replacers in the structure of isoxazolidine nucleotide analogues

Novel 5-arylcarbamoyl-2-methylisoxazolidin-3-yl-3-phosphonates
555
FIGURE 3 The preferred conformations of trans-isoxazolidines 11.
8, substituted benzo[d][1,3]dioxole derivatives were also selected, since nu-
merous natural and synthetic compounds containing this structural subunit
exhibited antiviral as well as anticancer activities.[45–47]
SCHEME 1 Retrosynthesis of (isoxazolidyn-3-yl)phosphonates 8 with a carbamoyl linker. (Color figure
available online).
RESULTS AND DISCUSSION
Chemistry
1,3-Dipolar cycloaddition of N -methyl-C-(diethoxyphosphoryl)nitrone
9
[34,35] with a series of heteroaromatic acrylamides 10 was employed for the
synthesis of isoxazolidines trans-11 and cis-12 (Scheme 2).
SCHEME 2 Reagents and conditions: (a) Et3N, acryloyl chloride, rt, 24 hours; (b) toluene, 70◦C,
24 hours, see Table 1.
To the best of our knowledge, all acrylamides, except for 10c-d, 10f-g,
10q, 10t, 10u, and 10w, have not been described in the literature. For the syn-
thesis of all acrylamides 10, the standard procedure employing acryloyl chlo-
ride in the presence of triethylamine was applied.[48] However, under these
conditions from 1H-3-aminopyrazole 14a and 1H-3-amino-5-methylpyrazole
14b, complex mixtures of products were formed. To alleviate this prob-
lem, compound 14a and 14b were reacted with Boc2O in the presence of

556
K. Kokosza et al.
sodium hydride in THF[49] to afford 15a, whereas in case of 14b a chromato-
graphically separable mixture (33:67) of two regioisomers 15b (19%) and
16b (10%) was obtained (Scheme 3). Even though isomer 16b was formed
predominantly, its isolation from the crude reaction mixture was tedious
and less effective. The remaining fractions of less polar 16b collected after
column chromatography were contaminated with unreacted Boc2O. Subse-
quent acroylation of 15a and 15b gave acrylamides 10a and 10b in 45 and
53% yield, respectively.
SCHEME 3 Reagents and conditions: (a) NaH, Boc2O, THF, 2 hours; (b) Et3N, acryloyl chloride, rt,
24 hours.
The 1,3-dipolar cycloadditions of the nitrone 9 with acrylamides 10a-
w were performed in toluene at 70◦C to give mixtures of isomeric (3-
diethoxyphosphoryl)isoxazolidines trans-11 and cis-12 with moderate to
good trans/cis diastereoselectivities (d.e. 58–76%) (Scheme 2, Table 1).
Crude mixtures of products were subjected to column chromatography to
provide almost all major trans-isomers (namely 11a-b, 11d-f, 11h-j, and 11l-w)
with moderate yields (Table 1). Attempts to obtain pure minor, cis-isomers
12 proved successful for 12f, 12l-n, 12r, and 12u-v only, but to achieve this
goal several separations of mixtures enriched in isoxazolidines 12 on silica
gel columns were necessary.
The relative configurations of the isoxazolidines 11a-w and 12a-w were
established taking advantage of our previous observations made on stereo-
chemistry of cycloaddition of N -methyl-C-diethoxyphosphorylated nitrone 9
with acrylamides derived from substituted anilines.[40] As expected, incorpo-
ration of hetereoaromatic substituents instead of substituted phenyl groups
in 10 had no influence on diastereoselectivities observed for the cycload-
dition of the nitrone 9 to acrylamides 10 (trans:cis 8:2). Moreover, similar
patterns for the respective isoxazolidine protons (H3, H4α, H4β, and H5)
were observed in the 1H NMR spectra in series of isoxazolidines trans-11a-w
and cis-12a-w as compared to the already described analogous trans- and cis-
cycloadducts obtained from 9 and N -arylacrylamides.[40] Indeed, detailed

Novel 5-arylcarbamoyl-2-methylisoxazolidin-3-yl-3-phosphonates
557
TABLE 1 Isoxazolidines 11 and 12 produced via Scheme 2.
Acrylamide 10
Entry
a
Ar
Ratio of 11: 12
Yield (%)
85:15
11a (58)a + 11a and 12a (16)b
b
c
82:18
83:17
11b (41)a + 11b and 12b (40)b
11c and 12c (88)b
d
e
88:12
87:13
11d (56)a + 11d and 12d (22)b
11e (60)a + 11e and 12e (15)b
f
84:16
11f (56)a + 12f (2)a + 11f and 12f (20)b
g
88:12
87:13
11g and 12g (98)b
h
11h (7)a + 11h and 12h (87)b
i
j
86:14
86:14
11i (30)a + 11i and 12i (53)b
11j (61)a + 11j and 1j2 (31)b
k
l
84:16
85:15
11k and 12k (96)b
11l (53)a + 12l (4)a + 11l and 12l (33)b
m
n
83:17
87:13
11m (17)a + 12m (4)a + 11m and 12m (61)b
11n (40)a + 12n (2)a + 11n and 12n (49)b
(Continued on next page)

558
K. Kokosza et al.
TABLE 1 Isoxazolidines 11 and 12 produced via Scheme 2. (Continued)
Acrylamide 10
Entry
o
Ar
Ratio of 11: 12
Yield (%)
84:16
11o (29)a + 11o and 12o (22)b
p
84:16
11p (53)a
q
r
s
85:15
78:22
87:13
11q (29)a + 11q and 12q (51)b
11r (60)a + 12r (6)a +11r and 12r (31)b
11s (73)a + 11s and 12s (21)b
t
84:16
84:16
11t (26)a + 11t and 12t (73)b
u
11u (46)a + 12u (4)a + 11u and 12u (25)b
v
85:15
80:20
11v (40)a + 12v (4)a + 11v and 12v (46)b
11w (39)a + 11w and 12w (35)b
w
aYield of pure isomer.
bYield of pure mixture of cis- and trans-isomers.
conformational analysis of major trans-isoxazolidines 11d-w based on val-
ues of vicinal HCCH,[50] HCCP,[51,52] and CCCP[53,54] coupling constants
[J CCCP = 8.8–9.5 Hz, J H3–H4α = 7.8–8.4 Hz, J H3–H4β = 8.4–9.2 Hz, J H4α–P
=
8.8–10.3 Hz, J H4β–P = 15.6–16.1 Hz, J H4α–H5 = 5.2–5.8 Hz, and J H4β–H5
=
8.4–9.2 Hz] revealed that the isoxazolidine ring in 11 exists in the E con-
3
formation having diethoxyphosphoryl group in the equatorial position and
carbamoyl substituents located pseudoequatorially.
Studies on Biological Activity
Antiviral Activity
5-Substituted 2-methylisoxazolidin-3-yl-3-phosphonates trans-11 and cis-
12 as well as the respective mixtures of trans-11/cis-12 enriched with cis-12

Novel 5-arylcarbamoyl-2-methylisoxazolidin-3-yl-3-phosphonates
559
were evaluated for their inhibitory activity against a wide variety of DNA and
RNA viruses, using the following cell-based assays: (a) in human embryonic
lung (HEL) cells: herpes simplex virus-1 (KOS), herpes simplex virus-2 (G),
vaccinia virus, vesicular stomatitis virus, herpes simplex virus-1 (TK− KOS
ACVr), varicella-zoster virus (VZV), and cytomegalovirus (CMV); (b) in HeLa
cell cultures: vesicular stomatitis virus, Coxsackie virus B4, and respiratory
syncytial virus; (c) in Vero cell cultures: para-influenza-3 virus, reovirus-1,
Sindbis virus, Coxsackie virus B4, and Punta Toro virus; (d) in CrFK cell
cultures: feline corona virus (FIPV), and feline herpes virus (FHV); (e) in
MDCK cell cultures: influenza A virus (H1N1 and H3N2 subtypes) and in-
fluenza B virus; and (f) in CEM cell cultures: human immunodeficiency virus
type 1 (HIV-1) and HIV-2. Ganciclovir, cidofovir, acyclovir, brivudin, (S)-9-
(2,3-dihydroxypropyl)adenine [(S)-DHPA], oseltamivir carboxylate, aman-
tadine, rimantadine, ribavirin, dextran sulfate (molecular weight 5000, DS-
5000), Hippeastrum hybrid agglutinin (HHA), and Urtica dioica agglutinin
(UDA) were used as the reference compounds. The antiviral activity was ex-
pressed as the EC50: the compound concentration required to reduce virus
plaque formation (VZV) by 50% or to reduce virus-induced cytopathogenic-
ity by 50% (other viruses). Unfortunately, no inhibitory activity against any
virus was detected for the evaluated compounds at 250 μM.
Cytotoxicity of the Tested Compounds
The cytotoxicity of the tested compounds toward the uninfected host
cells was defined as the minimum compound concentration (MCC) that
caused a microscopically detectable alteration of normal cell morphology.
None of the tested compounds affected cell morphology of HEL, HeLa,
Vero, MDCK, and CrFK cells at concentrations up to 100 μM.
Cytostatic Activity
The 50% cytostatic inhibitory concentration (IC50), causing a 50% de-
crease in cell proliferation, was determined against murine leukemia L1210,
human lymphocyte CEM, and human cervix carcinoma HeLa cells. Com-
pounds trans-11r and cis-12r, both having a 2,2-difluorobenzo[d][1,3]dioxol-
6-ylcarbamoyl substituent at C5 in the isoxazolidine ring, were found only
to slightly inhibit HeLa cell proliferation by 50% (IC50) at concentrations of
179 59 and 186 49 μM.
CONCLUSIONS
A
novel
series
of
5-arylcarbamoyl-2-methylisoxazolidin-3-yl-3-
phosphonates has been synthesized in good trans/cis (d.e. 58–76%)
diastereoselectivities via 1,3-dipolar cycloaddition of N -methyl-C-
(diethoxyphosphoryl)nitrone and selected heteroaromatic N -acrylamides.
Evaluation of the antiviral activity of the phosphonates cis-12 and trans-11

560
K. Kokosza et al.
was performed against a wide variety of DNA and RNA viruses. None of
the compounds was found active at concentrations up to 250 μM. Several
reasons may cause the lack of biological response from the virus-infected
cells including bioavailability and subsequent enzymatic hydrolysis followed
by phosphorylation of the corresponding phosphonic acids. Cytostatic
activity of cis- and trans-isoxazolidines was conducted on three tumor cell
lines (L1210, CEM and HeLa). Compounds cis-12r and trans-11r containing
a 2,2-difluorobenzo[d][1,3]dioxole moiety were cytostatic against human
cervix carcinoma HeLa cells at 189 and 179 μM (IC50), respectively.
EXPERIMENTAL
1H NMR spectra were taken in CDCl3 or CD3OD on the following spec-
trometers: Varian Mercury-300 and Bruker Avance III (600 MHz) with TMS
as internal standard. 13C NMR spectra were recorded for CDCl3 solution
on the Varian Mercur-300 machine at 75.5 MHz. 31P NMR spectra were
performed in CDCl3 solution on the Varian Mercury-300 at 121.5 MHz. IR
spectra were measured on an Infinity MI-60 FT-IR spectrometer. Melting
points were determined on a Boetius apparatus and are uncorrected. Ele-
mental analyses were performed by the Microanalytical Laboratory of this
Faculty on Perkin-Elmer PE 2400 CHNS analyzer. The following adsorbents
were used: column chromatography, Merck silica gel 60 (70–230 mesh);
analytical TLC, Merck TLC plastic sheets silica gel 60 F254.
Starting Materials. All solvents were dried according to the literature meth-
ods. The nitrone 9 was previously reported.[17]
General procedure for the preparation of acrylamides 10
To a solution of substituted heteroaromatic amine (1.00 mmol) in
dichloromethane, DMF or THF (2 mL) triethylamine (1.10 mmol) was
added. The mixture was cooled in an ice bath and acryloyl chloride
(1.05 mmol) was added dropwise. The reaction mixture was stirred for
24 hours at room temperature and extracted with water (3 × 3 mL). Subse-
quently, the aqueous layer was extracted with ethyl ether (3 × 5 mL). The
combined organic layers were dried over anhydrous MgSO4 and filtered.
After evaporation of solvents, the residue was purified on a silica column
with chloroform:methanol mixtures (100:1, 50:1 v/v) as eluents to afford
the respective acrylamides 10.
tert-Butyl 3-(acrylamido)-1H-pyrazole-1-carboxylate 10a
Yield: 45%; white amorphous solid (crystallized from chloro-
form/hexane) mp 135–136◦C; IR (KBr, cm−1) νmax: 3285, 3258, 1763, 1738,
1
1689, 1578, 1399, 1360, 1308, 1138, 965, 841, 764; H NMR (300 MHz,
CDCl3) δ: 8.44 (br s, 1H, NH), 8.00 (d, 1H, J = 2.8 Hz), 7.05 (d, 1H, J =
2.8 Hz), 6.45 (dd, 1H, J = 16.9, 1.0 Hz, CH CH2), 6.23 (dd, 1H, J = 16.9,
10.3 Hz, CH CH2), 5.82 (dd, 1H, J = 10.3, 1.0 Hz, CH CH2), 1.65 (s, 9H,

Novel 5-arylcarbamoyl-2-methylisoxazolidin-3-yl-3-phosphonates
561
3 × CH3); 13C NMR (75.5 MHz, CDCl3) δ: 163.63 (s, C(O)NH), 151.17 (s,
C(O)), 147.25, 131.71, 130.63 (s, CH CH2), 128.54 (s, CH CH2), 102.89,
85.80 (s, C(CH3)3), 28.12 (s, 3 × CH3). Anal. Calcd. for C11H15N3O3: C,
55.69; H, 6.37; N, 17.71; found: C, 55.39; H, 6.26; N, 17.43.
tert-Butyl 3-(acrylamido)-5-methyl-1H-pyrazole-1-carboxylate 10b
Yield: 53%; white amorphous solid (crystallized from chloro-
form/hexane) mp 145–146◦C; IR (KBr, cm−1) νmax: 3264, 2989, 1738, 1671,
1
1600, 1353, 1317, 1160, 1108, 980; H NMR (600 MHz, CDCl3) δ: 8.13 (br
s, 1H, NH), 6.82 (s, 1H, HC4), 6.43 (dd, 1H, J = 17.0, 0.8 Hz, CH CH2),
6.21 (dd, 1H, J = 17.0, 10.4 Hz, CH CH2), 5.81 (dd, 1H, J = 10.4, 0.8 Hz,
CH CH2), 2.55 (s, 3H, CH3), 1.67 (s, 9H, 3 × CH3); 13C NMR (151.0 MHz,
CDCl3) δ: 163.66 (s, C(O)NH), 149.53 (s, C(O)), 148.41, 144.70, 130.87 (s,
CH = CH2), 128.01 (s, CH CH2), 103.81, 85.21 (s, C(CH3), 27.80 (s, 3 ×
CH3), 14.88 (s, CH3). Anal. Calcd. for C12H17N3O3: C, 57.36; H, 6.82; N,
16.72; found: C, 57.10; H, 6.48; N, 16.82.
N-(4-Methylpyridin-2-yl)acrylamide 10e
Yield: 22%; white amorphous solid (crystallized from chloro-
form/hexane) mp 93–93.5◦C; IR (KBr, cm−1) νmax: 3185, 3009, 1686, 1614,
1
1582, 1417, 1210, 956, 834; H NMR (300 MHz, CDCl3) δ: 8.67 (br s, 1H,
NH), 8.17 (dd, 1H, J = 0.6, 0.6 Hz, HC3), 8.14 (dd, 1H, J = 5.2, 0.6 Hz,
HC6), 6.90 (dd, 1H, J = 5.2, 0.6 Hz, HC5), 6.47 (dd, 1H, J = 16.9, 1.4 Hz,
CH CH2), 6.27 (dd, 1H, J = 16.9, 10.1 Hz, CH = CH2), 5.80 (dd, 1H, J =
10.1, 1.4 Hz, CH = CH2), 2.39 (s, 3H, CH3); 13C NMR (75.5 MHz, CDCl3)
δ: 164.07 (s, C(O)), 152.07, 150.17, 146.90, 130.97 (s, CH = CH2), 128.34
(s, CH = CH2), 121.04, 115.67, 21.58 (s, CH3). Anal. Calcd. for C9H10N2O:
C, 66.65; H, 6.21; N, 17.27; found: C, 66.62; H, 6.09; N, 17.47.
N-(4-Methylpyrimidin-2-yl)acrylamide 10h
Yield: 19%; white amorphous solid (crystallized from chloro-
form/hexane) mp 133–135◦C; IR (KBr, cm−1) νmax: 2924, 1679, 1592, 1572,
1410, 1329, 954, 844; 1H NMR (300 MHz, CDCl3) δ: 8.47 (d, 1H, J = 5.0 Hz),
8.24 (br s, 1H, NH), 6.89 (dd, 1H, J = 16.9, 10.3 Hz, CH CH2), 6.88 (d,
1H, J = 5.0 Hz), 6.52 (dd, 1H, J = 16.9, 1.4 Hz, CH = CH2), 5.85 (dd, 1H, J
= 10.3, 1.4 Hz, CH CH2), 2.49 (s, 3H, CH3); 13C NMR (75.5 MHz, CDCl3)
δ: 168.98, 165.24 (s, C(O)), 157.75, 157.51, 130.78 (s, CH CH2), 129.33 (s,
CH CH2), 116.09, 24.42 (s, CH3). Anal. Calcd. for C8H9N3O: C, 58.88; H,
5.56; N, 25.75; found: C, 59.02; H, 5.26; N, 25.91.
N-(4-Methoxy-6-methylpyrimidin-2-yl)acrylamide 10i
Yield: 11%; white amorphous solid mp 88–93◦C; IR (KBr, cm−1) νmax
:
1
3196, 2990, 1694, 1615, 1542, 1467, 1354, 1186, 1065, 961; H NMR

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(300 MHz, CDCl3) δ: 8.00 (br s, 1H, NH), 7.07 (dd, 1H, J = 17.0, 10.3 Hz,
CH CH2), 6.51 (dd, 1H, J = 17.0, 1.6 Hz, CH CH2), 6.29 (s, 1H, HC5),
5.83 (dd, 1H, J = 10.3, 1.6 Hz, CH CH2), 3.95 (s, 3H, CH3O), 2.38 (s,
CH3); 13C NMR (75.5 MHz, CDCl3) δ: 170.67, 168.41, 165.26 (s, C(O)),
156.78, 130.69 (s, CH CH2), 129.01 (s, CH CH2), 101.78, 54.01 (s, OCH3),
23.84 (s, CH3). Anal. Calcd. for C9H11N3O2: C, 55.95; H, 5.74; N, 21.75;
found; C, 55.96; H, 5.64; N, 21.71.
N-(4,6-Dimethoxypyrimidin-2-yl)acrylamide 10j
Yield: 25%; white amorphous solid (crystallized from chloro-
form/hexane) mp 108–108.5◦C; IR (KBr, cm−1) νmax: 3335, 1674, 1607,
1576, 1420, 1376, 1317, 1224, 1081, 827, 797; 1H NMR (300 MHz, CDCl3) δ:
7.85 (br s, 1H, NH), 7.19 (dd, 1H, J = 17.1, 10.5 Hz, CH CH2), 6.51 (dd,
1H, J = 17.1, 1.6 Hz, CH CH2), 5.83 (dd, 1H, J = 10.5, 1.6 Hz, CH CH2),
5.77 (s, 1H, HC5), 3.92 (s, 6H, 2 × CH3O); 13C NMR (75.5 MHz, CDCl3) δ:
171.73, 165.38 (s, C(O)), 156.09, 130.48 (s, CH CH2), 129.34 (s, CH CH2),
85.12, 54.43 (s, OCH3). Anal. Calcd. for C9H11N3O3: C, 51.67; H, 5.30; N,
20.09; found: C, 51.66; H, 5.22; N, 20.02.
N-(Pyrazin-2-yl)acrylamide 10k
Yield: 21%; white amorphous solid (crystallized from chloro-
form/hexane) mp 155–157◦C; IR (KBr, cm−1) νmax: 3449, 3233, 3097, 1673,
1622, 1546, 1410, 1211, 846; 1H NMR (300 MHz, CDCl3) δ: 9.64 (d, 1H, J =
1.6 Hz, HC3), 8.38 (d, 1H, J = 2.6 Hz, HC6), 8.26 (dd, 1H, J = 2.6, 1.6 Hz,
HC5), 8.11 (br s, 1H, NH), 6.53 (dd, 1H, J = 16.9, 1.2 Hz, CH CH2),
6.32 (dd, 1H, J = 16.9, 10.3 Hz, CH CH2), 5.89 (dd, 1H, J = 10.3, 1.2 Hz,
CH CH2); 13C NMR (75.5 MHz, CDCl3) δ: 163.62 (s, C(O)), 148.26, 142.09,
140.42, 137.47, 130.17 (s, CH CH2), 129.84 (s, CH CH2). Anal. Calcd. for
C7H7N3O: C, 56.37; H, 4.73; N, 28.17; found: C, 56.28; H, 4.93; N, 28.21.
N-(1H-Indol-5-yl)acrylamide 10l
Yield: 67%; white amorphous solid (crystallized from chloro-
form/hexane) mp 123–124◦C; IR (KBr, cm−1) νmax: 3300, 3235, 1648,
1
1540, 1477, 1242, 811, 764, 730; H NMR (300 MHz, CD3OD) δ: 7.87–7.86
(m, 1H), 7.35–7.32 (m, 1H), 7.27–7.22 (m, 2H), 6.46 (dd, 1H, J = 16.9,
9.9 Hz, CH CH2), 6.42–6.41 (m, 1H), 6.34 (dd, 1H, J = 16.9, 2.1 Hz,
CH CH2), 5.73 (dd, 1H, J = 9.9, 2.1 Hz, CH CH2); 13C NMR (75.5 MHz,
CD3OD) δ: 165.99 (s, C(O)), 135.15, 132.70 (s, CH CH2), 131.19, 129.32,
126.97 (s, CH CH2), 126.62, 116.94, 113.70, 112.17, 102.58. Anal. Calcd. for
C11H10N2O: C, 70.95; H, 5.41; N, 15.04; found. C, 70.98; H, 5.56; N, 14.95.

Novel 5-arylcarbamoyl-2-methylisoxazolidin-3-yl-3-phosphonates
563
N-(2-Methyl-1H-indol-5-yl)acrylamide 10m
Yield: 36%; yellowish amorphous solid (crystallized from chloro-
form/hexane) mp 149–150◦C; IR (KBr, cm−1) νmax: 3330, 3260, 1645, 1537,
1406, 1225, 868, 773; 1H NMR (300 MHz, CD3OD) δ: 7.71–7.70 (m, 1H),
7.22–7.14 (m, 2H), 6.45 (dd, 1H, J = 17.0, 9.9 Hz, CH CH2), 6.33 (dd,
1H, J = 17.0, 2.1 Hz, CH CH2), 6.09–6.08 (m, 1H), 5.72 (dd, 1H, J =
9.9, 2.1 Hz, CH CH2), 2.40 (s, 3H, CH3); 13C NMR (75.5 MHz, CD3OD)
δ: 165.76 (s, C(O)), 137.65, 135.31, 132.59 (s, CH CH2), 130.82, 130.30,
126.73 (s, CH CH2), 115.62, 112.70, 111.12, 100.45, 13.56 (s, CH3). Anal.
Calcd. for C12H12N2O: C, 71.98; H, 6.04; N, 13.99; found: C, 71.76; H, 5.78;
N, 14.21.
N-(1H-Indol-6-yl)acrylamide 10n
Yield: 32%; white amorphous solid (crystallized from chloro-
form/hexane) mp 175–176◦C; IR (KBr, cm−1) νmax: 3290, 1649, 1524, 1233,
870, 811, 733; 1H NMR (300 MHz, CD3OD) δ: 8.00–7.98 (m, 1H), 7.49–7.46
(m, 1H), 7.20–7.19 (m, 1H), 7.06–7.02 (m, 1H), 6.47 (dd, 1H, J = 17.0,
10.0 Hz, CH CH2), 6.40–6.39 (m, 1H), 6.34 (dd, 1H, J = 17.0, 2.1 Hz,
CH CH2), 5.74 (dd, 1H, J = 10.0, 2.1 Hz, CH = CH2); 13C NMR (75.5 MHz,
CD3OD) δ: 165.88 (s, C(O)), 137.47, 133.57, 132.69 (s, CH CH2), 127.10 (s,
CH CH2), 126.71, 126.00, 121.18, 114.16, 104.65, 102.34. Anal. Calcd. for
C11H10N2O: C, 70.95; H, 5.41; N, 15.04; found. C, 70.86; H, 5.16; N, 15.34.
N-(1H-Benzo[d]imidazol-6-yl)acrylamide 10o
Yield: 28%; grey solid (crystallized from chloroform) mp > 250◦C; IR
(KBr, cm−1) νmax: 3407, 3064, 1671, 1603, 1428, 1410, 1236, 806; 1H NMR
(300 MHz, CD3OD) δ: 8.71 (s, 1H), 8.38–8.37 (m, 1H), 7.69–7.66 (m, 1H),
7.50–7.46 (m, 1H), 6.48 (dd, 1H, J = 17.1, 9.3 Hz, CH = CH2), 6.39 (dd, 1H,
J = 17.1, 2.6 Hz, CH = CH2), 5.81 (dd, 1H, J = 9.3, 2.6 Hz, CH = CH2); 13C
NMR (75.5 MHz, CD3OD) δ: 166.18, 142.11, 136.85, 135.65, 132.96, 132.39
(s, CH = CH2), 127.96 (s, CH = CH2), 119.08, 116.22, 106.86. Anal. Calcd.
for C10H9N3O: C, 64.16; H, 4.85; N, 22.45; found: C, 63.95; H, 5.05; N, 22.13.
N-(1,3-Dioxoisoindolin-5-yl)acrylamide 10p
Yield: 42%; yellow amorphous solid mp 211–212◦C; IR (KBr, cm−1) νmax
:
1
3359, 3240, 3062, 1766, 1720, 1614, 1554, 1361, 746; H NMR (300 MHz,
CD3OD) δ: 8.26 (d, 1H, J = 1.8 Hz, HC4), 7.95 (dd, 1H, J = 8.2, 1.8 Hz,
HC6), 7.78 (d, 1H, J = 8.2 Hz, HC7), 6.52–6.40 (m, 2H), 5.85 (dd, 1H,
J = 7.2, 4.6 Hz, CH CH2); 13C NMR (75.5 MHz, CD3OD) δ: 171.54 (s,
C(O)), 170.43 (s, C(O)), 166.26 (s, C(O)), 145.71, 137.04, 131.98 (s, CH =
CH2), 129.09 (s, CH CH2), 128.87, 125.84, 125.06, 114.95. Anal. Calcd. for
C11H8N2O3: C, 61.11; H, 3.73; N, 12.96; found; C, 60.82; H, 3.71; N, 12.86.

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N-(2,2-Difluorobenzo[d][1,3]dioxol-5-yl)acrylamide 10r
Yield: 43%; slightly yellowish amorphous solid (crystallized from chloro-
form) mp 175–176◦C; IR (KBr, cm−1) νmax: 3282, 3112, 1665, 1579, 1503,
1
1225, 1159, 1037, 958, 862, 807; H NMR (600 MHz, CDCl3) δ: 7.70 (br s,
1H), 7.33 (br s, 1H), 7.06 (dd, 1H, J = 8.5, 1.9 Hz, HC6), 7.02 (d, 1H, J =
8.5 Hz, HC7), 6.47 (dd, 1H, J = 16.8, 1.0 Hz, CH CH2), 6.25 (dd, 1H, J
= 16.8, 10.3 Hz, CH CH2), 5.83 (dd, 1H, J = 10.3, 1.0 Hz, CH = CH2);
13C NMR (75.5 MHz, CD3OD) δ: 165.96 (s, C(O)), 144.77, 141.10, 136.37,
133.06 (t, J = 250.2 Hz, CF2), 132.11 (s, CH CH2), 128.15 (s, CH CH2),
116.37, 110.49, 103.91. Anal. Calcd. for C10H7F2NO3: C, 52.87; H, 3.11; N,
6.17; found; C, 52.73; H, 2.99; N, 5.90.
N-(5-Acetylbenzo[d][1,3]dioxol-6-yl)acrylamide 10s
Yield: 40%; slightly orange amorphous solid (crystallized from chloro-
form) mp 137–140◦C; IR (KBr, cm−1) νmax: 3075, 2924, 1682, 1611, 1512,
1476, 1365, 1337, 1276, 1249, 1204, 1037, 787; 1H NMR (600 MHz, CDCl3)
δ: 8.53 (s, 1H), 7.31 (s, 1H), 6.44 (dd, 1H, J = 17.0, 0.9 Hz, CH = CH2), 6.32
(dd, 1H, J = 17.0, 10.3 Hz, CH = CH2), 6.07 (s, 2H, OCH2O), 5.81 (dd, 1H,
J = 10.3, 0.9 Hz, CH = CH2), 2.61 (s, 3H, CH3C(O)); 13C NMR (75.5 MHz,
CDCl3) δ: 200.59 (s, C(O)), 164.45 (s, C(O)NH), 152.88, 142.67, 139.25,
132.52 (s, CH = CH2), 127.40 (s, CH = CH2), 115.40, 109.80, 102.28, 101.66
(s, OCH2O), 28.92 (s, CH3C(O)). Anal. Calcd. for C12H11NO4: C, 61.80; H,
4.75; N, 6.01; found; C, 61.84; H, 4.88; N, 5.86.
N-(Thiazol-2-yl)acrylamide 10v
Yield: 27%; white (cream) amorphous solid (crystallized from chloro-
form/hexane) mp 145–146◦C; IR (KBr, cm−1) νmax: 3159, 2921, 2863, 1683,
1
1573, 1399, 1268, 1171, 973, 777; H NMR (300 MHz, CDCl3) δ: 7.52 (d,
1H, J = 3.6 Hz), 7.07 (d, 1H, J = 3.6 Hz), 6.63 (dd, 1H, J = 16.9, 1.2 Hz,
CH CH2), 6.45 (dd, 1H, J = 16.9, 10.3 Hz, CH CH2), 5.96 (dd, 1H, J =
10.3, 1.2 Hz, CH CH2); 13C NMR (75.5 MHz, CDCl3) δ: 163.31 (s, C(O)),
160.37, 136.38, 130.21 (s, CH CH2), 128.90 (s, CH CH2), 114.17. Anal.
Calcd. for C6H6N2OS: C, 46.74; H, 3.92; N, 18.17; found: C, 46.57; H, 3.64;
N, 18.07.
General Procedure for Preparation of Isoxazolidines 11 and 12
A mixture of the nitrone 9 (1.00 mmol), acrylamide 10 (1.00 mmol),
and toluene (2 mL) was stirred at 70◦C for 24 hours or until disappearance
of the starting nitrone (TLC). After evaporation of the solvent under re-
duced pressure, the crude products were purified on silica gel columns with
chloroform:methanol mixtures as eluents.

Novel 5-arylcarbamoyl-2-methylisoxazolidin-3-yl-3-phosphonates
565
Diethyl trans-5-(1-(tert-butoxycarbonyl)-1H-pyrazol-3-
ylcarbamoyl)-2-methylisoxazolidin-3-yl-3-phosphonate
trans-11a
White amorphous solid (crystallized from ether/hexane) mp 130–131◦C;
IR (KBr, cm−1) νmax: 3133, 2984, 1763, 1706, 1597, 1468, 1370, 1314, 1208,
1
1140, 1027, 957; H NMR (300 MHz, CDCl3) δ: 8.86 (br s, 1H, NH), 7.99
(d, 1H, J = 2.8 Hz), 6.98 (d, 1H, J = 2.8 Hz), 4.59 (dd, 1H, J = 8.6, 6.0 Hz,
HC5), 4.25–4.17 (m, 4H, 2 × CH2OP), 3.08–2.92 (m, 2H, HC3 and HβC4),
3.00 (s, 3H, CH3N), 2.84–2.70 (m, 1H, HαC4), 1.67 (s, 9H, C(CH3)3), 1.38
(t, 3H, J = 7.0 Hz, CH3CH2OP), 1.36 (t, 3H, J = 7.0 Hz, CH3CH2OP); 13
C
NMR (75.5 MHz, CDCl3) δ: 168.94 (s, C(O)NH), 149.48 (s, C(O)), 147.29,
131.79, 102.01, 85.90 (s, C(CH3)3), 75.99 (d, J = 9.2 Hz, C5), 63.66 (d, J =
166.3 Hz, C3), 63.60 (d, J = 6.3 Hz, CH2OP), 63.18 (d, J = 6.6 Hz, CH2OP),
46.85 (s, CH3N), 37.05 (s, C4), 28.19 (s, C(CH3)3), 16.81 (d, J = 4.9 Hz,
CH3CH2OP), 16.74 (d, J = 5.4 Hz, CH3CH2OP); 31P NMR (121.5 MHz,
CDCl3) δ: 21.23. Anal. Calcd. for C17H29N4O7P: C, 47.22; H, 6.76; N, 12.96;
found: C, 47.37; H, 6.81; N, 12.90.
Diethyl trans-5-(1-(tert-butoxycarbonyl)-5-methyl-1H-pyrazol-3-
ylcarbamoyl)-2-methylisoxazolidin-3-yl-3-phosphonate
trans-11b
White amorphous solid (crystallised from ether/hexane) mp 133–134◦C;
IR (KBr, cm−1) νmax: 2981, 2936, 1765, 1696, 1603, 1479, 1341, 1318, 1233,
1158, 1113, 1027, 978; 1H NMR (300 MHz, CDCl3) δ: 8.78 (br s, 1H, NH), 6.75
(s, 1H, HC4Ar), 4.62–4.55 (m, 1H, HC5), 4.26–4.15 (m, 4H, 2 × CH2OP),
3.08–2.92 (m, 2H, HC3 and HβC4), 3.01 (s, 3H, CH3N), 2.83–2.69 (m, 1H,
HαC4), 2.53 (s, 3H, CH3), 1.67 (s, 9H, C(CH3)3), 1.38 (t, 3H, J = 7.0 Hz,
CH3CH2OP), 1.36 (t, 3H, J = 7.0 Hz, CH3CH2OP); 13C NMR (75.5 MHz,
CDCl3) δ: 168.81 (s, C(O)NH), 148.37 (s, C(O)), 147.76, 144.71, 102.94,
85.42 (s, C(CH3)3), 75.94 (d, J = 9.2 Hz, C5), 63.53 (d, J = 165.9 Hz,
C3), 63.49 (d, J = 6.4 Hz, CH2OP), 62.68 (d, J = 6.9 Hz, CH2OP), 46.67 (s,
CH3N), 36.98 (s, C4), 28.17 (s, C(CH3)3), 16.69 (d, J = 5.2 Hz, CH3CH2OP),
16.63 (d, J = 5.4 Hz, CH3CH2OP), 15.14 (s, CH3); 31P NMR (121.5 MHz,
CDCl3) δ: 21.36. Anal. Calcd. for C18H31N4O7P: C, 48.43; H, 7.00; N, 12.55;
found: C, 48.53; H, 6.92; N, 12.66.
Diethyl trans-5-(2,5-dihydro-2,3-dimethyl-5-oxo-1-phenyl-1H-
pyrazol-4-ylcarbamoyl)-2-methylisoxazolidin-3-yl-3-phosphonate
trans-11c
Colorless oil. IR (film, cm−1) νmax: 3469, 2984, 1650, 1493, 1454, 1298,
1232, 1022, 968; (signals of trans-11c were extracted from the spectra of a
89:11 mixture of trans-11c and cis-12c); 1H NMR (300 MHz, CDCl3) δ: 8.15

566
K. Kokosza et al.
(br s, 1H, NH), 7.52–7.34 (m, 5H), 4.66 (dd, 1H, J = 8.9, 5.4 Hz, HC5),
4.24–4.16 (m, 4H, 2 × CH2OP), 3.28–3.16 (m, 1H, HC3), 3.17 (s, 3H,
CH3NNPh), 3.07 (s, 3H, CH3N), 3.04–2.78 (br m, 2H, HαC4 and HβC4),
2.31 (s, 3H, CH3C C), 1.36 (t, 3H, J = 7.1 Hz, CH3CH2OP), 1.35 (t, 3H,
J = 7.1 Hz, CH3CH2OP); 13C NMR (75.5 MHz, CDCl3) δ: 169.95, 161.29,
149.41, 134.37, 129.22, 127.02, 124.15, 107.38, 76.62 (d, J = 9.2 Hz, C5),
63.52 (d, J = 168.6 Hz, C3), 63.33 (d, J = 6.3 Hz, CH2OP), 62.63 (d, J =
6.9 Hz, CH2OP), 46.99 (s, CH3N), 45.93 (s, CH3NNPh), 36.18 (s, C4), 16.67
(d, J = 4.2 Hz, CH3CH2OP), 16.61 (d, J = 4.6 Hz, CH3CH2OP), 12.45 (s,
CH3); 31P NMR (121.5 MHz, CDCl3) δ: 21.53. Anal. Calcd. for C20H29N4O6P:
C, 53.09; H, 6.46; N, 12.38; found: C, 53.15; H, 6.44; N, 12.49. (obtained on
a 89:11 mixture of trans-11c and cis-12c).
Diethyl trans-5-(pyridin-2-ylcarbamoyl)-2-methylisoxazolidin-3-yl-
3-phosphonate trans-11d
White amorphous solid (crystallized from ether/hexane) mp 82–83◦C;
IR (KBr, cm−1) νmax: 3174, 2981, 1693, 1578, 1542, 1434, 1300, 1231, 1025,
1
787, 554; H NMR (300 MHz, CDCl3) δ: 8.75 (br s, 1H, NH), 8.32–8.29
(m, 1H), 8.22–8.19 (m, 1H), 7.75–7.70 (m, 1H), 7.11–7.06 (m, 1H), 4.61
(dd, 1H, J = 8.8, 5.7 Hz, HC5), 4.27–4.13 (m, 4H, 2 × CH2OP), 3.11–3.04
(m, 1H, HC3), 3.03 (s, 3H, CH3N), 3.01 (dddd, 1H, J = 15.9, 12.7, 8.8,
8.8 Hz, HβC4), 2.82 (dddd, 1H, J = 12.7, 9.0, 8.2, 5.7 Hz, HαC4), 1.36 (t,
3H, J = 7.2 Hz, CH3CH2OP), 1.35 (t, 3H, J = 7.0 Hz, CH3CH2OP); 13C
NMR (75.5 MHz, CDCl3) δ: 169.22 (s, C(O)), 150.26, 147.96, 138.38, 120.34,
113.96, 76.21 (d, J = 9.2 Hz, C5), 63.50 (d, J = 169.8 Hz, C3), 63.47 (d, J =
6.3 Hz, CH2OP), 62.64 (d, J = 6.9 Hz, CH2OP), 46.79 (s, CH3N), 36.87 (s,
C4), 16.68 (d, J = 5.1 Hz, CH3CH2OP), 16.60 (d, J = 5.4 Hz, CH3CH2OP);
31P NMR (121.5 MHz, CDCl3) δ: 21.43. Anal. Calcd. for C14H22N3O5P: C,
48.98; H, 6.46; N, 12.24; found: C, 48.99; H, 6.40; N, 12.47.
Diethyl trans-5-(4-methylpyridin-2-ylcarbamoyl)-2-methylis
oxazolidin-3-yl-3-phosphonate trans-11e
White amorphous solid (crystallized from ether/hexane) mp 89–91◦C;
IR (KBr, cm−1) νmax: 3204, 3062, 2987, 1693, 1564, 1418, 1207, 1029, 836, 590;
1H NMR (300 MHz, CDCl3) δ: 8.70 (br s, 1H, NH), 8.16–8.15 (m, 1H), 8.05
(s, 1H), 6.91–6.89 (m, 1H), 4.60 (dd, 1H, J = 8.8, 5.4 Hz, HC5), 4.26–4.13
(m, 4H, 2 × CH2OP), 3.08–3.02 (m, 1H, HC3), 3.02 (s, 3H, CH3N), 3.00
(dddd, 1H, J = 15.7, 12.5, 8.8, 8.8 Hz, HβC4), 2.81 (dddd, 1H, J = 12.5, 8.8,
8.1, 5.4 Hz, HαC4), 2.38 (s, 3H, CH3), 1.36 (t, 3H, J = 7.2 Hz, CH3CH2OP),
1.34 (t, 3H, J = 7.0 Hz, CH3CH2OP); 13C NMR (75.5 MHz, CDCl3) δ: 169.03
(s, C(O)), 150.08, 149.80, 147.21, 121.30, 114.34, 76.56 (d, J = 9.2 Hz, C5),

Novel 5-arylcarbamoyl-2-methylisoxazolidin-3-yl-3-phosphonates
567
63.28 (d, J = 167.2 Hz, C3), 63.27 (d, J = 6.6 Hz, CH2OP), 62.46 (d, J
= 7.1 Hz, CH2OP), 36.71 (s, C4), 21.33 (s, CH3), 16.41 (d, J = 5.7 Hz,
CH3CH2OP), 16.48 (d, J = 4.9 Hz, CH3CH2OP); 31P NMR (121.5 MHz,
CDCl3) δ: 21.45. Anal. Calcd. for C15H24N3O5P: C, 50.42; H, 6.77; N, 11.76;
found: C, 50.46; H, 6.92; N, 11.93.
Diethyl trans-5-(5-methylpyridin-2-ylcarbamoyl)-2-methylis
oxazolidin-3-yl-3-phosphonate trans-11f
White solid (crystallized from ether/hexane) mp 91–92◦C. IR (KBr,
1
cm−1) νmax: 3240, 2987, 1689, 1537, 1300, 1242, 1055, 1026, 575; H NMR
(300 MHz, CDCl3) δ: 8.69 (br s, 1H, NH), 8.12–8.08 (m, 2H), 7.55–7.52
(m, 1H), 4.59 (dd, 1H, J = 8.8, 5.8 Hz, HC5), 4.26–4.13 (m, 4H, 2 ×
CH2OP), 3.08–3.01 (m, 1H, HC3), 3.03 (s, 3H, CH3N), 3.00 (dddd, 1H,
J = 15.9, 12.5, 8.8, 8.8 Hz, HβC4), 2.81 (dddd, 1H, J = 12.5, 9.0, 7.8, 5.8 Hz,
HαC4), 2.31 (s, 3H, CH3), 1.37 (t, 3H, J = 6.9 Hz, CH3CH2OP), 1.35 (t,
3H, J = 6.9 Hz, CH3CH2OP); 13C NMR (75.5 MHz, CDCl3) δ: 169.00 (s,
C(O)), 148.10, 147.86, 138.88, 129.75, 113.47, 76.22 (d, J = 9.4 Hz, C5),
63.51 (d, J = 168.6 Hz, C3), 63.47 (d, J = 6.6 Hz, CH2OP), 62.64 (d, J
= 6.9 Hz, CH2OP), 46.84 (s, CH3N), 36.92 (s, C4), 18.03 (s, CH3), 16.70
(d, J = 5.1 Hz, CH3CH2OP), 16.62 (d, J = 5.4 Hz, CH3CH2OP); 31P NMR
(121.5 MHz, CDCl3) δ: 21.48. Anal. Calcd. for C15H24N3O5P: C, 50.42; H,
6.77; N, 11.76; found: C, 50.46; H, 6.71; N, 11.88.
Diethyl cis-5-(5-methylpyridin-2-ylcarbamoyl)-2-methylis
oxazolidin-3-yl-3-phosphonate cis-12f
Colorless oil; IR (film, cm−1) νmax: 3205, 3063, 2988, 1694, 1613, 1565,
1
1549, 1419, 1239, 1208, 1056, 1029, 981, 836; H NMR (300 MHz, CDCl3)
δ: 9.02 (br s, 1H, NH), 8.10–8.06 (m, 2H), 7.49–7.46 (m, 1H), 4.54 (dd,
1H, J = 8.6, 3.6 Hz, HC5), 4.15–3.98 (m, 4H, 2 × CH2OP), 3.02–2.79 (m,
3H, HC3, HαC4 and HβC4), 2.97 (d, 3H, J = 1.0 Hz, CH3N), 2.26 (s,
3H, CH3), 1.24 (t, 3H, J = 7.0 Hz, CH3CH2OP), 1.11 (t, 3H, J = 7.0 Hz,
CH3CH2OP); 13C NMR signals of cis-12f were extracted from the spectrum
of a 64:36 mixture of trans-11f and cis-12f, 13C NMR (75.5 MHz, CDCl3) δ:
170.84 (s, C(O)), 148.56, 147.90, 138.87, 129.39, 113.35, 75.58 (d, J = 8.1 Hz,
C5), 63.77 (d, J = 6.4 Hz, CH2OP), 63.60 (d, J = 167.7 Hz, C3), 62.56 (d,
J = 6.9 Hz, CH2OP), 46.22 (s, CH3N), 36.95 (s, C4), 18.13 (s, CH3), 16.62
(d, J = 6.0 Hz, CH3CH2OP), 16.47 (d, J = 5.9 Hz, CH3CH2OP);. 31P NMR
(121.5 MHz, CDCl3) δ: 21.60. Anal. Calcd. for C15H24N3O5P: C, 50.42; H,
6.77; N, 11.76; found: C, 50.57; H, 6.90; N, 11.93.

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Diethyl trans-5-(pyrimidin-2-ylcarbamoyl)-2-methylisoxazolidin-3-
yl-3-phosphonate trans-11g
Colorless oil; IR (film, cm−1) νmax: 3432, 2984, 1715, 1580, 1513, 1438,
1416, 1229, 1051, 1024; (signals of trans-11g were extracted from the spectra
1
of a 93:7 mixture of trans-11g and cis-12g); H NMR (600 MHz, CDCl3) δ:
8.97 (br s, 1H, NH), 8.68 (d, 2H, J = 4.9 Hz, HC4Ar and HC6Ar), 7.10 (t,
1H, J = 4.9 Hz, HC5Ar), 4.69 (dd, 1H, J = 8.9, 5.3 Hz, HC5), 4.26–4.15
(m, 4H, 2 × CH2OP), 3.13–3.08 (m, 1H, HC3), 3.05 (s, 3H, CH3N), 3.04
(dddd, 1H, J = 16.1, 13.1, 8.9, 8.9 Hz, HβC4), 2.90 (dddd, 1H, J = 13.1,
9.3, 8.0, 5.3 Hz, HαC4), 1.38 (t, 3H, J = 7.1 Hz, CH3CH2OP), 1.36 (t, 3H, J
= 7.1 Hz, CH3CH2OP); 13C NMR (151.0 MHz, CDCl3) δ: 168.80 (s, C(O)),
158.51, 156.71, 117.29, 76.46 (d, J = 9.3 Hz, C5), 63.45 (d, J = 168.5 Hz,
C3), 63.38 (d, J = 6.5 Hz, CH2OP), 62.58 (d, J = 6.8 Hz, CH2OP), 46.72
(s, CH3N), 36.72 (s, C4), 16.49 (d, J = 5.7 Hz, CH3CH2OP), 16.41 (d, J =
6.1 Hz, CH3CH2OP); 31P NMR (243.0 MHz, CDCl3) δ: 20.19. Anal. Calcd.
for C13H21N4O5P: C, 45.35; H, 6.15; N, 16.27; found: C, 45.19; H, 6.24; N,
16.37 (obtained on a 93:7 mixture of trans-11g and cis-12g).
Diethyl trans-5-(4-methylpyrimidin-2-ylcarbamoyl)-2-methylis
oxazolidin-3-yl-3-phosphonate trans-11h
Colorless oil; IR (film, cm−1) νmax: 3401, 2984, 1718, 1594, 1530, 1443,
1
1402, 1233, 1052, 1025, 971; H NMR (600 MHz, CDCl3) δ: 8.87 (br s, 1H,
NH), 8.54 (d, 1H, J = 5.0 Hz), 6.96 (d, 1H, J = 5.0 Hz), 4.71–4.65 (br m,
1H, HC5), 4.26–4.17 (m, 4H, 2 × CH2OP), 3.14–3.07 (m, 1H, HC3), 3.06
(s, 3H, CH3N), 3.04 (dddd, 1H, J = 16.0, 13.0, 8.9, 8.9 Hz, HβC4), 2.90
(dddd, 1H, J = 13.0, 8.9, 8.1, 5.3 Hz, HαC4), 2.53 (s, 3H, CH3), 1.38 (t, 3H,
J = 7.0 Hz, CH3CH2OP), 1.36 (t, 3H, J = 7.0 Hz, CH3CH2OP); 13C NMR
(151.0 MHz, CDCl3) δ: 169.13, 168.81 (s, C(O)), 157.96, 156.46, 116.93,
76.47 (d, J = 9.3 Hz, C5), 63.45 (d, J = 169.2 Hz, C3), 63.39 (d, J = 6.5 Hz,
CH2OP), 62.55 (d, J = 6.8 Hz, CH2OP), 46.73 (s, CH3N), 36.75 (s, C4),
16.48 (d, J = 5.9 Hz, CH3CH2OP), 16.42 (d, J = 5.8 Hz, CH3CH2OP); 31
P
NMR (243.0 MHz, CDCl3) δ: 20.27. Anal. Calcd. for C14H23N4O5P: C, 46.93;
H, 6.47; N, 15.64; found: C, 46.85; H, 6.71; N, 15.76.
Diethyl trans-5-(4-methoxy-6-methylpyrimidin-2-ylcarbamoyl)-2-
methylisoxazolidin-3-yl-3-phosphonate trans-11i
White amorphous solid (crystallized from ether/hexane) mp 90–91◦C;
IR (KBr, cm−1) νmax: 3386, 2983, 1717, 1601, 1512, 1422, 1381, 1249, 1055,
1018, 960; 1H NMR (300 MHz, CDCl3) δ: 8.69 (br s, 1H, NH), 6.33 (s, 1H,
HC5Ar), 4.74–4.66 (br m, 1H, HC5), 4.26–4.12 (m, 4H, 2 × CH2OP), 3.97

Novel 5-arylcarbamoyl-2-methylisoxazolidin-3-yl-3-phosphonates
569
(s, 3H, CH3O), 3.13–3.09 (m, 1H, HC3), 3.03 (s, 3H, CH3N), 3.03 (dddd,
1H, J = 16.1, 13.0, 8.9, 8.9 Hz, HβC4), 2.91 (dddd, 1H, J = 13.0, 8.8, 8.3,
5.2 Hz, HαC4), 2.41 (s, 3H, CH3), 1.36 (t, 3H, J = 7.0 Hz, CH3CH2OP), 1.34
(t, 3H, J = 7.0 Hz, CH3CH2OP); 13C NMR (151.0 MHz, CDCl3) δ: 170.95,
168.73, 168.73 (s, C(O)), 155.86, 102.61, 76.54 (d, J = 9.1 Hz, C5), 63.45
(d, J = 167.4 Hz, C3), 63.33 (d, J = 6.2 Hz, CH2OP), 62.54 (d, J = 6.7 Hz,
CH2OP), 53.88 (s, CH3O), 46.73 (s, CH3N), 36.57 (s, C4), 23.85 (s, CH3),
16.48 (d, J = 5.6 Hz, CH3CH2OP), 16.42 (d, J = 6.2 Hz, CH3CH2OP); 31
P
NMR (121.5 MHz, CDCl3) δ: 20.80. Anal. Calcd. for C15H25N4O6P: C, 46.39;
H, 6.49; N, 14.43; found: C, 46.45; H, 6.30; N, 14.48.
Diethyl trans-5-(4,6-dimethoxypyrimidin-2-ylcarbamoyl)-2-
methylisoxazolidin-3-yl-3-phosphonate trans-11j
White amorphous solid (crystallized from ether/hexane) mp 98–99◦C;
IR (KBr, cm−1) νmax: 3399, 1726, 1609, 1569, 1512, 1447, 1412, 1372, 1198,
1
1171, 1058, 1018, 946; H NMR (600 MHz, CDCl3) δ: 8.61 (br s, 1H, NH),
5.84 (s, 1H, HC5Ar), 4.74 (br s, HC5), 4.26–4.17 (m, 4H, 2 × CH2OP),
3.97 (s, 6H, CH3O), 3.16–3.09 (m, 1H, HC3), 3.06 (s, 3H, CH3N), 3.02
(dddd, 1H, J = 16.0, 13.0, 8.9, 8.9 Hz, HβC4), 2.91 (dddd, 1H, J = 13.0,
8.9, 8.3, 5.2 Hz, HαC4), 1.39 (t, 3H, J = 7.2 Hz, CH3CH2OP), 1.37 (t, 3H,
J = 7.1 Hz, CH3CH2OP); 13C NMR (151.0 MHz, CDCl3) δ: 172.16, 168.76
(s, C(O)), 155.27, 85.66, 76.57 (d, J = 9.0 Hz, C5), 63.45 (d, J = 169.0 Hz,
C3), 63.31 (d, J = 6.3 Hz, CH2OP), 62.56 (d, J = 6.7 Hz, CH2OP), 46.73
(s, CH3N), 36.47 (s, C4), 16.48 (d, J = 5.7 Hz, CH3CH2OP), 16.43 (d, J =
5.7 Hz, CH3CH2OP); 31P NMR (243.0 MHz, CDCl3) δ: 20.40. Anal. Calcd.
for C15H25N4O7P: C, 44.55; H, 6.23; N, 13.86; found: C, 44.81; H, 6.05; N,
13.93.
Diethyl trans-5-(pyrazin-2-ylcarbamoyl)-2-methylisoxazolidin-3-yl-
3-phosphonate trans-11k
Colorless oil. IR (film, cm−1) νmax: 3385, 2982, 1703, 1543, 1414, 1296,
1232, 1053, 1023, 969; (signals of trans-11k were extracted from the spectra
1
of a 96:4 mixture of trans-11k and cis-12k); H NMR (600 MHz, CDCl3) δ:
9.56 (d, 1H, J = 1.5 Hz, HC3Ar), 8.77 (br s, 1H, NH), 8.41 (d, 1H, J = 2.5 Hz,
HC6Ar), 8.30 (dd, 1H, J = 2.5, 1.5 Hz, HC5Ar), 4.67 (dd, 1H, J = 9.0, 5.5 Hz,
HC5), 4.26–4.17 (m, 4H, 2 × CH2OP), 3.13–3.07 (m, 1H, HC3), 3.05 (s,
3H, CH3N), 3.04 (dddd, 1H, J = 16.1, 13.0, 8.8, 8.8 Hz, HβC4), 2.85 (dddd,
1H, J = 13.0, 9.7, 8.3, 5.6 Hz, HαC4), 1.38 (t, 3H, J = 7.1 Hz, CH3CH2OP),
1.37 (t, 3H, J = 7.1 Hz, CH3CH2OP); 13C NMR (75.5 MHz, CDCl3) δ: 169.29
(s, C(O)), 147.14, 142.23, 140.83, 136.89, 76.20 (d, J = 8.9 Hz, C5), 63.55
(d, J = 167.8 Hz, C3), 63.54 (d, J = 6.6 Hz, CH2OP), 62.79 (d, J = 6.9 Hz,
CH2OP), 46.80 (s, CH3N), 37.00 (s, C4), 16.72 (d, J = 5.4 Hz, CH3CH2OP),

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16.65 (d, J = 5.1 Hz, CH3CH2OP); 31P NMR (243.0 MHz, CDCl3) δ:
20.10. Anal. Calcd. for C13H21N4O5P: C, 45.35; H, 6.15; N, 16.27; found:
C, 45.29; H, 6.29; N, 16.32 (obtained on a 96:4 mixture of trans-11k and
cis-12k).
Diethyl cis-5-(pyrazin-2-ylcarbamoyl)-2-methylisoxazolidin-3-yl-3-
phosphonate cis-12k
Colorless oil; IR (film, cm−1) νmax: 3385, 3210, 2983, 1704, 1536, 1414,
1297, 1233, 1027, 971; (signals of cis-12k were extracted from the spectra
1
of a 14:86 mixture of trans-11k and cis-12k); H NMR (600 MHz, CDCl3)
δ: 9.57 (d, 1H, J = 1.5 Hz, HC3Ar), 9.24 (brs, 1H, NH), 8.38 (d, 1H,
J = 2.5 Hz, HC6Ar), 8.30 (dd, 1H, J = 2.5, 1.5 Hz, HC5Ar), 4.66–4.63
(br m, 1H, HC5), 4.27–4.06 (m, 4H, 2 × CH2OP), 3.08–2.99 (m, 2H,
HC3 and HβC4), 3.03 (d, 3H, J = 0.7 Hz, CH3N), 2.93–2.87 (m, 1H,
HαC4), 1.31 (t, 3H, J = 7.0 Hz, CH3CH2OP), 1.20 (t, 3H, J = 7.0 Hz,
CH3CH2OP); 13C NMR (151.0 MHz, CDCl3) δ: 171.06 (s, C(O)), 147.68,
142.25, 140.42, 136.81, 75.56 (d, J = 7.7 Hz, C5), 63.51 (d, J = 170.2 Hz,
C3), 63.34 (d, J = 6.7 Hz, CH2OP), 62.59 (d, J = 7.1 Hz, CH2OP),
45.94 (s, CH3N), 36.57 (s, C4), 16.36 (d, J = 5.6 Hz, CH3CH2OP), 16.23
(d, J = 5.7 Hz, CH3CH2OP); 31P NMR (243.0 MHz, CDCl3) δ: 20.43.
Anal. Calcd. for C13H21N4O5P: C, 45.35; H, 6.15; N, 16.27; found: C,
45.29; H, 6.07; N, 16.16 (obtained on a 14:86 mixture of trans-11k and
cis-12k).
Diethyl trans-5-(1H-indol-5-ylcarbamoyl)-2-methylisoxazolidin-3-
yl-3-phosphonate trans-11l
Yellowish oil; IR (film, cm−1) νmax: 3284, 2983, 1669, 1547, 1480, 1231,
1
1051, 972, 762; H NMR (300 MHz, CDCl3) δ: 8.35 (br s, 1H, NH), 8.21
(br s, 1H, C(O)NH), 7.90–7.89 (m, 1H), 7.36–7.27 (m, 1H), 7.25–7.21 (m,
2H), 6.53–6.51 (m, 1H), 4.64 (dd, 1H, J = 8.9, 5.6 Hz, HC5), 4.27–4.13
(m, 4H, 2 × CH2OP), 3.15–3.06 (m, 1H, HC3), 3.04 (s, 3H, CH3N), 3.00
(dddd, 1H, J = 15.8, 13.0, 8.9, 8.9 Hz, HβC4), 2.88 (dddd, 1H, J = 13.0,
9.1, 8.1, 5.6 Hz, HαC4), 1.37 (t, 3H, J = 7.0 Hz, CH3CH2OP), 1.35 (t, 3H,
J = 7.0 Hz, CH3CH2OP); 13C NMR (75.5 MHz, CDCl3) δ: 168.65 (s, C(O)),
133.61, 129.10, 128.00, 125.65, 115.80, 112.50, 111.47, 102.44, 76.63 (d, J =
9.2 Hz, C5), 63.57 (d, J = 166.3 Hz, C3), 63.56 (d, J = 6.6 Hz, CH2OP), 62.79
(d, J = 6.9 Hz, CH2OP), 46.99 (s, CH3N), 36.74 (s, C4), 16.75 (d, J = 5.2 Hz,
CH3CH2OP), 16.66 (d, J = 5.4 Hz, CH3CH2OP); 31P NMR (121.5 MHz,
CDCl3) δ: 21.59. Anal. Calcd. for C17H24N3O5P: C, 53.54; H, 6.34; N, 11.02;
found: C, 53.48; H, 6.19; N, 11.18.

Novel 5-arylcarbamoyl-2-methylisoxazolidin-3-yl-3-phosphonates
571
Diethyl cis-5-(1H-indol-5-ylcarbamoyl)-2-methylisoxazolidin-3-yl-
3-phosphonate cis-12l
Yellowish oil; IR (film, cm−1) νmax: 3281, 2984, 2927, 1668, 1548, 1481,
1232, 1024, 975, 730; 1H NMR (300 MHz, CDCl3) δ: 8.66 (br s, 1H, C(O)NH),
8.22 (br s, 1H, NH), 7.93–7.92 (m, 1H), 7.35–7.27 (m, 2H), 7.21–7.19 (m,
1H), 6.52–6.51 (m, 1H), 4.62 (dd, 1H, J = 8.5, 5.2 Hz, HC5), 4.21–4.06
(m, 4H, 2 × CH2OP), 3.11–2.79 (m, 3H, HC3, HαC4 and HβC4), 2.99 (s,
3H, CH3N), 1.29 (t, 3H, J = 7.2 Hz, CH3CH2OP), 1.19 (t, 3H, J = 7.0 Hz,
CH3CH2OP); 13C NMR signals of cis-12l were extracted from the spectrum
of a 56:44 mixture of trans-11l and cis-12l, 13C NMR (75.5 MHz, CDCl3) δ:
169.68 (s, C(O)), 133.35, 129.83, 128.01, 125.35, 115.83, 112.15, 111.33,
102.65, 75.92 (d, J = 7.8 Hz, C5), 64.02 (d, J = 168.6 Hz, C3), 63.63 (d, J =
6.4 Hz, CH2OP), 62.89 (d, J = 6.1 Hz, CH2OP), 46.35 (s, CH3N), 36.84 (s,
C4), 16.71 (d, J = 5.4 Hz, CH3CH2OP), 16.63 (d, J = 5.5 Hz, CH3CH2OP);
31P NMR (121.5 MHz, CDCl3) δ: 22.06. Anal. Calcd. for C17H24N3O5P: C,
53.54; H, 6.34; N, 11.02; found: C, 53.66; H, 6.12; N, 10.81.
Diethyl trans-5-(2-methyl-1H-indol-5-ylcarbamoyl)-2-methylis
oxazolidin-3-yl-3-phosphonate trans-11m
Yellowish oil; IR (film, cm−1) νmax: 3279, 2984, 1669, 1543, 1483, 1231,
1
1025, 971, 778; H NMR (300 MHz, CDCl3) δ: 8.17 (br s, 1H, C(O)NH),
7.99 (br s, 1H, NH), 7.74–7.73 (m, 1H), 7.24–7.16 (m, 2H), 6.18–6.19 (m,
1H), 4.59 (dd, 1H, J = 8.8, 5.4 Hz, HC5), 4.27–4.13 (m, 4H, 2 × CH2OP),
3.14–3.01 (m, 1H, HC3), 3.04 (s, 3H, CH3N), 3.00 (dddd, 1H, J = 15.7,
12.8, 8.8, 8.8 Hz, HβC4), 2.87 (dddd, 1H, J = 12.8, 9.1, 8.2, 5.4 Hz, HαC4),
2,44 (s, 3H, CH3), 1.36 (t, 3H, J = 7.2 Hz, CH3CH2OP), 1.35 (t, 3H, J
= 6.9 Hz, CH3CH2OP); 13C NMR (75.5 MHz, CDCl3) δ: 168.51 (s, C(O)),
136.63, 133.83, 129.20, 129.03, 114.52, 111.46, 110.52, 100.40, 76.61 (d, J =
9.2 Hz, C5), 63.59 (d, J = 169.8 Hz, C3), 63.56 (d, J = 6.6 Hz, CH2OP),
62.75 (d, J = 6.9 Hz, CH2OP), 46.97 (s, CH3N), 36.79 (s, C4), 16.73 (d, J =
5.1 Hz, CH3CH2OP), 16.66 (d, J = 5.4 Hz, CH3CH2OP), 13.93 (s, CH3); 31
P
NMR (121.5 MHz, CDCl3) δ: 21.60. Anal. Calcd. for C18H26N3O5P: C, 54.68;
H, 6.63; N, 10.63; found: C, 54.86; H, 6.76; N, 10.52.
Diethyl cis-5-(2-methyl-1H-indol-5-ylcarbamoyl)-2-methylis
oxazolidin-3-yl-3-phosphonate cis-12m
Yellowish oil; IR (film, cm−1) νmax: 3281, 2984, 2926, 1668, 1544, 1484,
1
1452, 1230, 1026, 972, 755; H NMR (300 MHz, CDCl3) δ: 8.61 (br s, 1H,
C(O)NH), 7.97 (br s, 1H, NH), 7.77 (s, 1H), 7.21–7.20 (m, 2H), 6.17 (s,
1H), 4.62 (dd, 1H, J = 8.3, 5.0 Hz, HC5), 4.22–4.03 (m, 4H, 2 × CH2OP),
3.07–2.83 (m, 3H, HC3, HαC4 and HβC4), 2.99 (s, 3H, CH3N), 2,42 (s,
3H, CH3), 1.30 (t, 3H, J = 7.0 Hz, CH3CH2OP), 1.19 (t, 3H, J = 7.0 Hz,

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K. Kokosza et al.
CH3CH2OP); 13C NMR signals of cis-12m were extracted from the spectrum
of a 34:66 mixture of trans-11m and cis-12m, 13C NMR (151.0 MHz, CDCl3)
δ: 169.56 (s, C(O)), 136.09, 133.53, 129.95, 129.29, 114.61, 111.16, 110.20,
100.69, 75.82 (d, J = 7.6 Hz, C5), 64.03 (d, J = 168.7 Hz, C3), 63.37 (d, J =
6.6 Hz, CH2OP), 62.59 (d, J = 7.1 Hz, CH2OP), 46.15 (s, CH3N), 36.79 (s,
C4), 16.40 (d, J = 5.5 Hz, CH3CH2OP), 16.34 (d, J = 5.6 Hz, CH3CH2OP),
13.73 (s, CH3); 31P NMR (121.5 MHz, CDCl3) δ: 22.03. Anal. Calcd. for
C18H26N3O5P: C, 54.68; H, 6.63; N, 10.63; found: C, 54.79; H, 6.64; N, 10.75.
Diethyl trans-5-(1H-indol-6-ylcarbamoyl)-2-methylis
oxazolidin-3-yl-3-phosphonate trans-11n
Colorless oil; IR (film, cm−1) νmax: 3291, 2983, 1674, 1536, 1230, 1050,
1
1024, 969; H NMR (300 MHz, CDCl3) δ: 8.43 (br s, 1H, C(O)NH), 8.29
(br s, 1H, NH), 8.11–8.10 (m, 1H), 7.58–7.55 (m, 1H), 7.21–7.19 (m, 1H),
6.93–6.89 (m, 1H), 6.52–6.50 (m, 1H), 4.65 (dd, 1H, J = 8.5, 5.5 Hz, HC5),
4.27–4.14 (m, 4H, 2 × CH2OP), 3.15–3.02 (m, 1H, HC3), 3.05 (dddd, 1H,
J = 15.7, 13.0, 8.5, 8.5 Hz, HβC4), 3.04 (s, 3H, CH3N), 2.87 (dddd, 1H, J
= 13.0, 9.8, 8.4, 5.5 Hz, HαC4), 1.36 (t, 3H, J = 7.0 Hz, CH3CH2OP), 1.35
(t, 3H, J = 7.0 Hz, CH3CH2OP); 13C NMR (75.5 MHz, CDCl3) δ: 168.59 (s,
C(O)), 136.01, 131.36, 125.30, 125.07, 120.73, 113.01, 103.32, 102.08, 76.75
(d, J = 8.8 Hz, C5), 63.58 (d, J = 167.2 Hz, C3), 63.52 (d, J = 6.6 Hz,
CH2OP), 62.92 (d, J = 6.9 Hz, CH2OP), 47.04 (s, CH3N), 36.55 (s, C4),
16.74 (d, J = 5.7 Hz, CH3CH2OP), 16.67 (d, J = 4.3 Hz, CH3CH2OP); 31
P
NMR (121.5 MHz, CDCl3) δ: 21.60. Anal. Calcd. for C17H24N3O5P × 2H2O:
C, 48.92; H, 6.76; N, 10.07; found: C, 48.91; H, 6.91; N, 9.82.
Diethyl cis-5-(1H-indol-6-ylcarbamoyl)-2-methylisoxazolidin-3-yl-
3-phosphonate cis-12n
Colorless oil; IR (film, cm−1) νmax: 3272, 2984, 1675, 1598, 1536, 1456,
1231, 1025, 971, 808; 1H NMR (300 MHz, CDCl3) δ: 8.77 (br s, 1H, C(O)NH),
8.32 (br s, 1H, NH), 8.13–8.12 (m, 1H), 7.55–7.53 (m, 1H), 7.19–7.17 (m,
1H), 6.96–6.93 (m, 1H), 6.51–6.49 (m, 1H), 4.63 (dd, 1H, J = 8.6, 5.1 Hz,
HC5), 4.21–4.02 (m, 4H, 2 × CH2OP), 3.09–2.83 (m, 3H, HC3, HαC4
and HβC4), 2.99 (d, 3H, J = 0.8 Hz, CH3N), 1.30 (t, 3H, J = 7.0 Hz,
CH3CH2OP), 1.18 (t, 3H, J = 7.0 Hz, CH3CH2OP); 13C NMR signals of
cis-12n were extracted from the spectrum of a 77:23 mixture of trans-11n and
cis-12n, 13C NMR (75.5 MHz, CDCl3) δ: 169.72 (s, C(O)), 136.04, 131.89,
124.98, 124.75, 120.64, 113.06, 102.97, 102.06, 75.95 (d, J = 7.4 Hz, C5),
63.58 (d, J = 168.1 Hz, C3), 63.58 (d, J = 6.5 Hz, CH2OP), 62.91 (d, J
= 6.9 Hz, CH2OP), 46.37 (s, CH3N), 36.76 (s, C4), 16.64 (d, J = 5.2 Hz,
CH3CH2OP), 16.57 (d, J = 5.4 Hz, CH3CH2OP); 31P NMR (121.5 MHz,

Novel 5-arylcarbamoyl-2-methylisoxazolidin-3-yl-3-phosphonates
573
CDCl3) δ: 21.93. Anal. Calcd. for C17H24N3O5P: C, 53.54; H, 6.34; N, 11.02;
found: C, 53.64; H, 6.06; N, 11.01.
Diethyl trans-5-(1H-benzo[d]imidazol-6-ylcarbamoyl)-2-
methylisoxazolidin-3-yl-3-phosphonate trans-11o
Yellowish oil; IR (film, cm−1) νmax: 3192, 2989, 1680, 1604, 1548, 1488,
1
1449, 1395, 1295, 1230, 1025, 970; H NMR (300 MHz, CDCl3) δ: 8.54 (br
s, 1H, C(O)NH), 8.14 (d, 1H, J = 1.6 Hz), 8.03 (s, 1H), 7.62 (d, 1H, J =
8.6 Hz), 7.21 (dd, 1H, J = 8.6, 1.6 Hz), 4.68 (dd, 1H, J = 8.6, 5.8 Hz, HC5),
4.26–4.15 (m, 4H, 2 × CH2OP), 3.19–3.09 (m, 1H, HC3), 3.03 (dddd, 1H,
J = 16.1, 12.6, 8.6, 8.6 Hz, HβC4), 3.02 (s, 3H, CH3N), 2.89 (dddd, 1H, J
= 12.6, 9.9, 8.3, 5.8 Hz, HαC4), 1.36 (t, 3H, J = 7.0 Hz, CH3CH2OP), 1.35
(t, 3H, J = 7.0 Hz, CH3CH2OP); 13C NMR (75.5 MHz, CDCl3) δ: 168.96 (s,
C(O)), 141.88, 137.10, 136.46, 132.20, 117.12, 116.21, 106.50, 76.85 (d, J ∼
9 Hz, C5), 63.62 (d, J = 167.5 Hz, C3), 63.57 (d, J = 6.6 Hz, CH2OP), 63.11
(d, J = 7.2 Hz, CH2OP), 47.02 (s, CH3N), 36.45 (s, C4), 16.76 (d, J = 5.5 Hz,
CH3CH2OP), 16.71 (d, J = 5.2 Hz, CH3CH2OP); 31P NMR (121.5 MHz,
CDCl3) δ: 21.92. Anal. Calcd. for C16H23N4O5P x 2H2O: C, 45.93; H, 6.50;
N, 13.39; found: C, 45.95; H, 6.53; N, 13.33.
Diethyl trans-5-(1,3-dioxoisoindolin-5-ylcarbamoyl)-2-
methylisoxazolidin-3-yl-3-phosphonate trans-11p
Yellowish oil; IR (film, cm−1) νmax: 3286, 2984, 1721, 1682, 1614, 1582,
1
1482, 1435, 1361, 1230, 1023, 973; H NMR (300 MHz, CDCl3) δ: 8.72 (br
s, 1H, C(O)NHC(O)), 8.31 (br s, 1H, C(O)NH), 8.12 (d, 1H, J = 1.7 Hz,
HC4Ar), 8.05 (dd, 1H, J = 8.2, 1.7 Hz, HC6Ar), 7.85 (d, 1H, J = 8.2 Hz,
HC7Ar), 4.70 (dd, 1H, J = 8.6, 5.6 Hz, HC5), 4.29–4.17 (m, 4H, 2 × CH2OP),
3.25–3.15 (m, 1H, HC3), 3.04 (dddd, 1H, J = 15.8, 12.8, 8.4, 8.4 Hz, HβC4),
2.87 (dddd, 1H, J = 12.8, 10.3, 8.2, 5.4 Hz, HαC4), 3.04 (s, 3H, CH3N), 1.39
(t, 3H, J = 7.0 Hz, CH3CH2OP), 1.38 (t, 3H, J = 7.0 Hz, CH3CH2OP); 13
C
NMR (151.0 MHz, CDCl3) δ: 169.29 (s, C(O)), 168.08 (s, C(O)), 167.88 (s,
C(O)), 142.78, 134.34, 127.99, 124.76, 124.41, 114.47, 76.60 (d, J = 8.8 Hz,
C5), 63.48 (d, J = 167.1 Hz, C3), 63.42 (d, J = 6.6 Hz, CH2OP), 63.01 (d,
J = 6.7 Hz, CH2OP), 46.48 (s, CH3N), 36.10 (s, C4), 16.49 (d, J = 6.3 Hz,
CH3CH2OP), 16.44 (d, J = 6.4 Hz, CH3CH2OP); 31P NMR (121.5 MHz,
CDCl3) δ: 21.60. Anal. Calcd. for C17H22N3O7P × H2O: C, 47.55; H, 5.63; N,
9.79; found: C, 47.46; H, 5.53; N, 9.57.
Diethyl trans-5-(benzo[d][1,3]dioxol-5-ylcarbamoyl)-2-
methylisoxazolidin-3-yl-3-phosphonate trans-11q
Yellow oil; IR (film, cm−1) νmax: 3285, 2985, 2908, 1680, 1537, 1503, 1449,
1229, 1037, 971, 755; 1H NMR (600 MHz, CDCl3) δ: 8.08 (br s, 1H, NH), 7.28

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(d, 1H, J = 2.1 Hz, HC4Ar), 6.86 (dd, 1H, J = 8.3, 2.1 Hz, HC6Ar), 6.78 (d,
1H, J = 8.3 Hz, HC7Ar), 5.98 (s, 2H, OCH2O), 4.61 (dd, 1H, J = 8.9, 5.5 Hz,
HC5), 4.26–4.18 (m, 4H, 2 × CH2OP), 3.11–3.06 (m, 1H, HC3), 3.03 (s, 3H,
CH3N), 3.01 (dddd, 1H, J = 16.0, 13.0, 8.9, 8.9 Hz, HβC4), 2.85 (dddd, 1H,
J = 13.0, 8.6, 8.2, 5.5 Hz, HαC4), 1.39 (t, 3H, J = 7.1 Hz, CH3CH2OP), 1.37
(t, 3H, J = 7.1 Hz, CH3CH2OP); 13C NMR (75.5 MHz, CDCl3) δ: 168.53 (s,
C(O)), 147.89, 144.69, 131.10, 113.12, 108.19, 102.64, 101.45 (s, OCH2O),
76.45 (d, J = 9.2 Hz, C5), 63.59 (d, J = 169.8 Hz, C3), 63.15 (d, J = 6.6 Hz,
CH2OP), 62.75 (d, J = 6.9 Hz, CH2OP), 46.95 (s, CH3N), 36.70 (s, C4),
16.77 (d, J = 5.4 Hz, CH3CH2OP), 16.70 (d, J = 5.4 Hz, CH3CH2OP); 31
P
NMR (243.0 MHz, CDCl3) δ: 20.30. Anal. Calcd. for C16H23N2O7P × 2H2O:
C, 45.50; H, 6.44; N, 6.63; found: C, 45.48; H, 6.30; N, 6.92.
Diethyl trans-5-(2,2-difluorobenzo[d][1,3]dioxol-5-ylcarbamoyl)-2-
methylisoxazolidin-3-yl-3-phosphonate trans-11r
White amorphous solid (crystallized from ether/hexane) mp 105–106◦C;
IR (KBr, cm−1) νmax: 3252, 3083, 2986, 1691, 1538, 1501, 1450, 1239, 1156,
1
964; H NMR (600 MHz, CDCl3) δ: 8.25 (br s, 1H, NH), 7.66 (d, 1H, J =
2.0 Hz, HC4Ar), 7.06 (dd, 1H, J = 8.5, 2.0 Hz, HC6Ar), 7.02 (d, 1H, J = 8.5 Hz,
HC7Ar), 4.62 (dd, 1H, J = 8.8, 5.5 Hz, HC5), 4.25–4.17 (m, 4H, 2 × CH2OP),
3.13–3.06 (m, 1H, HC3), 3.03 (s, 3H, CH3N), 3.01 (dddd, 1H, J = 16.1, 13.0,
8.8, 8.8 Hz, HβC4), 2.83 (dddd, 1H, J = 13.0, 9.5, 8.2, 5.5 Hz, HαC4), 1.38 (t,
3H, J = 7.1 Hz, CH3CH2OP), 1.37 (t, 3H, J = 7.1 Hz, CH3CH2OP); 13C NMR
(151.0 MHz, CDCl3) δ: 168.85 (s, C(O)), 143.84, 140.39, 133.19, 131.74 (t,
J = 255.5 Hz, CF2), 114.76, 109.28, 103.03, 76.36 (d, J = 9.0 Hz, C5), 63.48
(d, J = 167.3 Hz, C3), 63.29 (d, J = 6.5 Hz, CH2OP), 62.64 (d, J = 7.1 Hz,
CH2OP), 46.62 (s, CH3N), 36.27 (s, C4), 16.43 (d, J = 5.7 Hz, CH3CH2OP),
16.37 (d, J = 5.8 Hz, CH3CH2OP); 31P NMR (243.0 MHz, CDCl3) δ: 20.19.
Anal. Calcd. for C16H21F2N2O7P: C, 45.50; H, 5.01; N, 6.63; found: C, 45.32;
H, 5.17; N, 6.38.
Diethyl cis-5-(2,2-difluorobenzo[d][1,3]dioxol-5-ylcarbamoyl)-2-
methylisoxazolidin-3-yl-3-phosphonate cis-12r
Colorless oil; IR (film, cm−1) νmax: 3198, 3073, 1698, 1550, 1523, 1508,
1
1434, 1213, 1161, 1125, 1026; H NMR (600 MHz, CDCl3) δ: 8.99 (br s,
1H, NH), 7.70 (d, 1H, J = 2.0 Hz, HC4Ar), 7.12 (dd, 1H, J = 8.6, 2.0 Hz,
HC6Ar), 7.00 (d, 1H, J = 8.6 Hz, HC7Ar), 4.65 (dd, 1H, J = 9.4, 4.4 Hz,
HC5), 4.25–4.07 (m, 4H, 2 × CH2OP), 3.13–3.03 (m, 2H, HC3 and HβC4),
2.96 (s, 3H, CH3N), 2.83–2.76 (m, 1H, HαC4), 1.35 (t, 3H, J = 7.0 Hz,
CH3CH2OP), 1.26 (t, 3H, J = 7.1 Hz, CH3CH2OP); 13C NMR (151.0 MHz,
CDCl3) δ: 169.85 (s, C(O)), 143.88, 140.13, 133.86, 131.79 (t, J = 255.1 Hz,
CF2), 114.50, 109.23, 102.75, 76.03 (d, J = 6.5 Hz, C5), 63.68 (d, J = 170.5 Hz,

Novel 5-arylcarbamoyl-2-methylisoxazolidin-3-yl-3-phosphonates
575
C3), 63.11 (d, J = 6.4 Hz, CH2OP), 62.97 (d, J = 6.7 Hz, CH2OP), 46.01
(s, CH3N), 36.15 (s, C4), 16.44 (d, J = 5.7 Hz, CH3CH2OP), 16.35 (d, J =
5.8 Hz, CH3CH2OP); 31P NMR (243.0 MHz, CDCl3) δ: 21.16. Anal. Calcd.
for C16H21F2N2O7P: C, 45.50; H, 5.01; N, 6.63; found: C, 45.75; H, 4.90; N,
6.40.
Diethyl trans-5-(5-acetylbenzo[d][1,3]dioxol-6-ylcarbamoyl)-2-
methylisoxazolidin-3-yl-3-phosphonate trans-11s
Yellowish amorphous solid mp 94–95◦C; IR (KBr, cm−1) νmax: 3444, 2980,
1
2914, 1686, 1648, 1611, 1518, 1248, 1049, 1023, 960; H NMR (300 MHz,
CDCl3) δ: 12.63 (br s, 1H, NH), 8.41 (s, 1H), 7.29 (s, 1H), 6.05 (s, 2H,
OCH2O), 4.59 (dd, 1H, J = 9.1, 5.5 Hz, HC5), 4.28–4.15 (m, 4H, 2 ×
CH2OP), 3.15 (s, 3H, CH3N), 3.13–3.05 (m, 1H, HC3), 3.02 (dddd, 1H, J
= 16.0, 12.8, 9.1, 9.1 Hz, HβC4), 2.76 (dddd, 1H, J = 12.8, 9.9, 8.0, 5.5 Hz,
HαC4), 2.58 (s, CH3C(O)), 1.37 (t, 3H, J = 7.0 Hz, CH3CH2OP), 1.34 (t, 3H,
J = 7.0 Hz, CH3CH2OP); 13C NMR (75.5 MHz, CDCl3) δ: 199.83 (s, C(O)),
170.69 (s, C(O)NH), 152.56, 143.00, 137.58, 116.30, 109.86, 102.33, 101.82
(s, OCH2O), 76.60 (d, J = 10.0 Hz, C5), 63.41 (d, J = 169.8 Hz, C3), 63.55
(d, J = 6.3 Hz, CH2OP), 62.64 (d, J = 6.9 Hz, CH2OP), 46.59 (s, CH3N),
37.74 (s, C4), 28.90 (s, CH3C(O)), 16.81 (d, J = 4.9 Hz, CH3CH2OP), 16.74
(d, J = 5.7 Hz, CH3CH2OP); 31P NMR (121.5 MHz, CDCl3) δ: 21.60. Anal.
Calcd. for C18H25N2O8P: C, 50.47; H, 5.88; N, 6.54; found: C, 50.70; H, 5.60;
N, 6.47.
Diethyl cis-5-(5-acetylbenzo[d][1,3]dioxol-6-ylcarbamoyl)-2-
methylisoxazolidin-3-yl-3-phosphonate cis-12s
Yellowish oil; IR (film, cm−1) νmax: 3453, 2980, 2911, 1686, 1645, 1615,
1513, 1240, 1053, 1023, 964; (signals of cis-12s were extracted from the spec-
tra of a 50:50 mixture of trans-11s and cis-12s); 1H NMR (300 MHz, CDCl3)
δ: 12.86 (br s, 1H, NH), 8.47 (s, 1H), 7.30 (s, 1H), 6.05 (s, 2H, OCH2O),
4.56–4.53 (m, 1H, HC5), 4.16–4.01 (m, 4H, 2 × CH2OP), 3.05–2.91 (br
m, 2H, HC3 and HβC4), 3.11 (s, 3H, CH3N), 2.80–2.74 (m, 1H, HαC4),
2.58 (s, CH3C(O)), 1.29 (t, 3H, J = 7.1 Hz, CH3CH2OP), 1.13 (t, 3H, J =
7.1 Hz, CH3CH2OP); 13C NMR (151.0 MHz, CDCl3) δ: 199.41 (s, C(O)),
172.20 (s, C(O)NH), 152.43, 142.64, 137.86, 116.27, 109.27, 102.08, 101.37
(s, OCH2O), 75.43 (d, J = 8.6 Hz, C5), 63.33 (d, J = 166.2 Hz, C3), 63.44
(d, J = 6.4 Hz, CH2OP), 62.15 (d, J = 7.2 Hz, CH2OP), 46.33 (s, CH3N),
36.74 (s, C4), 27.84 (s, CH3C(O)), 16.35 (d, J = 6.1 Hz, CH3CH2OP), 16.18
(d, J = 5.7 Hz, CH3CH2OP); 31P NMR (121.5 MHz, CDCl3) δ: 22.00. Anal.
Calcd. for C18H25N2O8P: C, 50.47; H, 5.88; N, 6.54; found: C, 50.52; H, 5.63;
N, 6.30 (obtained on a 50:50 mixture of trans-11s and cis-12s).

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Diethyl trans-5-(2,3-dihydrobenzo[b][1,4]dioxin-6-ylcarbamoyl)-2-
methylisoxazolidin-3-yl-3-phosphonate trans-11t
White amorphous solid mp 105–106◦C; IR (film, cm−1) νmax: 3273, 2983,
1685, 1509, 1302, 1228, 1053, 1026, 969; 1H NMR (600 MHz, CDCl3) δ: 8.02
(br s, 1H, NH), 7.21 (d, 1H, J = 2.5 Hz, HC5Ar), 6.96 (dd, 1H, J = 8.7, 2.5 Hz,
HC7Ar), 6.84 (d, 1H, J = 8.7 Hz, HC8Ar), 4.61 (dd, 1H, J = 8.9, 5.3 Hz, HC5),
4.28–4.26 (m, 4H, 2 × OCH2), 4.26–4.17 (m, 4H, 2 × CH2OP), 3.11–3.05
(m, 1H, HC3), 3.03 (s, 3H, CH3N), 3.00 (dddd, 1H, J = 16.0, 12.9, 8.9,
8.9 Hz, HβC4), 2.85 (dddd, 1H, J = 12.9, 9.0, 8.1, 5.3 Hz, HαC4), 1.39
(t, 3H, J = 7.1 Hz, CH3CH2OP), 1.37 (t, 3H, J = 7.1 Hz, CH3CH2OP);
13C NMR (151.0 MHz, CDCl3) δ: 168.49 (s, C(O)), 143.59, 140.82, 130.55,
117.28, 113.40, 109.65, 76.36 (d, J = 9.4 Hz, C5), 64.42 (s, CH2O), 64.28 (s,
CH2O), 63.52 (d, J = 169.9 Hz, C3), 63.34 (d, J = 6.4 Hz, CH2OP), 62.53
(d, J = 6.7 Hz, CH2OP), 46.73 (s, CH3N), 36.55 (s, C4), 16.49 (d, J = 5.7 Hz,
CH3CH2OP), 16.43 (d, J = 5.6 Hz, CH3CH2OP); 31P NMR (243.0 MHz,
CDCl3) δ: 20.33. Anal. Calcd. for C17H25N2O7P: C, 51.00; H, 6.29; N, 7.00;
found: C, 51.03; H, 6.44; N, 6.97.
Diethyl trans-5-((benzo[d][1,3]dioxol-5-yl)methylcarbamoyl)-2-
methylisoxazolidin-3-yl-3-phosphonate trans-11u
Yellowish oil; IR (film, cm−1) νmax: 3292, 2982, 2911, 1668, 1444, 1239,
1037, 808; 1H NMR (300 MHz, CDCl3) δ: 7.79–7.74 (m, 3H), 6.71 (br s, 1H,
NH), 5.96 (s, 2H, OCH2O), 4.51 (dd, 1H, J = 8.7, 5.6 Hz, HC5), 4.36 (d,
2H, J = 5.7 Hz, CH2NH), 4.25–4.12 (m, 4H, 2 × CH2OP), 3.02–2.93 (m,
1H, HC3), 2.94 (dddd, 1H, J = 15.6, 12.6, 8.7, 8.7 Hz, HβC4), 2.90 (d, 3H,
J = 0.8 Hz, CH3N), 2.73 (dddd, 1H, J = 12.6, 9.4, 8.1, 5.6 Hz, HαC4), 1.35
(t, 3H, J = 7.0 Hz, CH3CH2OP), 1.34 (t, 3H, J = 7.0 Hz, CH3CH2OP); 13
C
NMR (75.5 MHz, CDCl3) δ: 170.39 (s, C(O)), 147.90, 147.03, 131.56, 121.03,
108.32, 108.29, 101.13, 76.24 (d, J = 9.2 Hz, C5), 63.51 (d, J = 169.8 Hz,
C3), 63.44 (d, J = 6.6 Hz, CH2OP), 62.54 (d, J = 6.9 Hz, CH2OP), 46.75 (s,
CH3N), 43.06 (s, CH2NH), 36.68 (s, C4), 16.65 (d, J = 5.4 Hz, CH3CH2OP),
16.58 (d, J = 5.2 Hz, CH3CH2OP); 31P NMR (121.5 MHz, CDCl3) δ: 21.63.
Anal. Calcd. for C17H25N2O7P: C, 51.00; H, 6.29; N, 7.00; found: C, 49.93;
H, 6.06; N, 6.91.
Diethyl cis-5-((benzo[d][1,3]dioxol-5-yl)methylcarbamoyl)-2-
methylisoxazolidin-3-yl-3-phosphonate cis-12u
Yellowish oil; IR (film, cm−1) νmax: 3419, 3318, 2983, 1665, 1531, 1503,
1
1444, 1238, 1038, 971, 809; H NMR (300 MHz, CDCl3) δ: 7.13 (br s, 1H,
NH), 6.79–6.74 (m, 3H), 5.93 (s, 2H, OCH2O), 4.52 (dd, 1H, J = 8.7, 5.4 Hz,
HC5), 4.43 (dAB, 1H, J = 14.7, 5.8 Hz, CH2bNH), 4.30 (dAB, 1H, J = 14.7,
6.4 Hz, CH2aNH), 4.20–4.02 (m, 4H, 2 × CH2OP), 3.03–2.85 (m, 2H, HC3

Novel 5-arylcarbamoyl-2-methylisoxazolidin-3-yl-3-phosphonates
577
and HβC4), 2.89 (d, 3H, J = 1.0 Hz, CH3N), 2.82–2.63 (m, 1H, HαC4), 1.32
(t, 3H, J = 7.0 Hz, CH3CH2OP), 1.28 (t, 3H, J = 7.0 Hz, CH3CH2OP); 13
C
NMR signals of cis-12u were extracted from the spectrum of a 45:55 mixture
of trans-11u and cis-12u, 13C NMR (75.5 MHz, CDCl3) δ: 171.68 (s, (CO)),
147.99, 147.14, 132.01, 121.15, 108.46, 108.32, 101.25, 75.40 (d, J = 8.4 Hz,
C5), 64.16 (d, J = 167.9 Hz, C3), 63.27 (d, J = 6.5 Hz, CH2OP), 62.83 (d, J
= 6.8 Hz, CH2OP), 46.25 (s, CH3N), 42.85 (s, CH2NH), 36.84 (s, C4), 16.79
(d, J = 4.7 Hz, CH3CH2OP), 16.72 (d, J = 5.5 Hz, CH3CH2OP); 31P NMR
(121.5 MHz, CDCl3) δ: 22.12. Anal. Calcd. for C17H25N2O7P: C, 51.00; H,
6.29; N, 7.00; found: C, 49.70; H, 6.07; N, 7.11.
Diethyl trans-5-(thiazol-2-ylcarbamoyl)-2-methylisox
azolidin-3-yl-3-phosphonate trans-11v
White amorphous solid (crystallized from ether/hexane) mp 124–125◦C;
IR (KBr, cm−1) νmax: 2986, 2896, 1700, 1564, 1325, 1286, 1238, 1170, 1020,
973; 1H NMR (300 MHz, CDCl3) δ: 7.52 (d, 1H, J = 3.5 Hz), 7.04 (d, 1H, J =
3.5 Hz), 4.71 (dd, 1H, J = 8.6, 5.2 Hz, HC5), 4.27–4.13 (m, 4H, 2 × CH2OP),
3.13–3.04 (m, 1H, HC3), 3.02 (dddd, 1H, J = 15.6, 12.7, 8.6, 8.6 Hz, HβC4),
3.01 (s, 3H, CH3N), 2.84 (dddd, 1H, J = 12.7, 9.4, 8.3, 5.2 Hz, HαC4),1.37
(t, 3H, J = 7.0 Hz, CH3CH2OP), 1.35 (t, 3H, J = 7.1 Hz, CH3CH2OP);
13C NMR (75.5 MHz, CDCl3) δ: 168.54 (s, C(O)), 157.99, 137.73, 113.85,
76.05 (d, J = 8.5 Hz, C5), 63.67 (d, J = 167.4 Hz, C3), 63.36 (d, J = 6.4 Hz,
CH2OP), 62.80 (d, J = 6.8 Hz, CH2OP), 46.91 (s, CH3N), 36.00 (s, C4), 16.73
(d, J = 5.2 Hz, CH3CH2OP), 16.66 (d, J = 5.3 Hz, CH3CH2OP); 31P NMR
(121.5 MHz, CDCl3) δ: 21.22. Anal. Calcd. for C12H20N3O5PS: C, 41.26; H,
5.77; N, 12.03; found: C, 41.47; H, 5.64; N, 12.17.
Diethyl cis-5-(thiazol-2-ylcarbamoyl)-2-methylisoxazolidin-3-yl-3-
phosphonate cis-12v
Colorless oil; IR (film, cm−1) νmax: 3438, 2987, 2927, 1700, 1565, 1286,
1239, 1020, 973; 1H NMR (300 MHz, CDCl3) δ: 7.47 (d, 1H, J = 3.5 Hz), 7.00
(d, 1H, J = 3.5 Hz), 4.69 (dd, 1H, J = 5.6, 3.5 Hz, HC5), 4.19–4.00 (m, 4H,
2 × CH2OP), 3.10–2.78 (m, 3H, HC3, HαC4 and HβC4), 2.99 (d, 3H, J =
0.9 Hz, CH3N), 1.28 (t, 3H, J = 7.0 Hz, CH3CH2OP), 1.17 (t, 3H, J = 7.1 Hz,
CH3CH2OP); 13C NMR signals of cis-12v were extracted from the spectrum
of a 58:42 mixture of trans-11v and cis-12v, 13C NMR (151.0 MHz, CDCl3) δ:
170.24 (s, C(O)), 157.44, 137.75, 113.63, 75.16 (d, J = 7.6 Hz, C5), 63.55
(d, J = 170.8 Hz, C3), 63.30 (d, J = 6.5 Hz, CH2OP), 62.68 (d, J = 6.6 Hz,
CH2OP), 45.86 (s, CH3N), 36.15 (s, C4), 16.32 (d, J = 5.9 Hz, CH3CH2OP),
16.18 (d, J = 5.7 Hz, CH3CH2OP); 31P NMR (121.5 MHz, CDCl3) δ: 21.50.
Anal. Calcd. for C12H20N3O5PS: C, 41.26; H, 5.77; N, 12.03; found: C, 41.51;
H, 5.89; N, 12.21.

578
K. Kokosza et al.
Diethyl trans-5-(benzo[d]thiazol-6-ylcarbamoyl)-2-methylis
oxazolidin-3-yl-3-phosphonate trans-11w
Colorless oil; IR (film, cm−1) νmax: 3257,3067, 2982, 2910, 1690, 1581,
1530, 1476, 1446, 1401, 1293, 1052, 970; 1H NMR (600 MHz, CDCl3) δ: 8.96
(s, 1H, HC2Ar), 8.59 (d, 1H, J = 2.1 Hz, HC7Ar), 8.38 (br s, 1H, NH), 8.10
(d, 1H, J = 8.7 Hz, HC4Ar), 7.44 (dd, 1H, J = 8.7, 2.1 Hz, HC5Ar), 4.68 (dd,
1H, J = 8.9, 5.4 Hz, HC5), 4.28–4.19 (m, 4H, 2 × CH2OP), 3.15–3.09 (m,
1H, HC3), 3.07 (s, 3H, CH3N), 3.05 (dddd, 1H, J = 16.1, 13.0, 8.9, 8.9 Hz,
HβC4), 2.88 (dddd, 1H, J = 13.0, 9.1, 8.0, 5.4 Hz, HαC4), 1.40 (t, 3H, J
= 7.1 Hz, CH3CH2OP), 1.38 (t, 3H, J = 7.1 Hz, CH3CH2OP); 13C NMR
(151.0 MHz, CDCl3) δ: 168.98 (s, C(O)), 153.61, 150.31, 134.82, 134.70,
123.69, 119.01, 112.58, 76.43 (d, J = 9.0 Hz, C5), 63.54 (d, J = 169.2 Hz,
C3), 63.34 (d, J = 6.5 Hz, CH2OP), 62.61 (d, J = 6.7 Hz, CH2OP), 46.71
(s, CH3N), 36.48 (s, C4), 16.49 (d, J = 5.6 Hz, CH3CH2OP), 16.43 (d, J =
5.6 Hz, CH3CH2OP); 31P NMR (243.0 MHz, CDCl3) δ: 20.18. Anal. Calcd.
for C16H22N3O5PS: C, 48.11; H, 5.55; N, 10.52; found: C, 48.01; H, 5.37; N,
10.32.
Antiviral Activity Assays
The compounds were evaluated against the following viruses: herpes sim-
plex virus type 1 (HSV-1) strain KOS, thymidine kinase-deficient (TK−) HSV-
1 KOS strain resistant to ACV (ACVr), herpes simplex virus type 2 (HSV-2)
strains Lyons and G, varicella-zoster virus (VZV) strain Oka, TK− VZV strain
07−1, human cytomegalovirus (HCMV) strains AD-169 and Davis, vaccinia
virus Lederle strain, respiratory syncytial virus (RSV) strain Long, vesicular
stomatitis virus (VSV), Coxsackie B4, Parainfluenza 3, Influenza virus A (sub-
types H1N1, H3N2), influenza virus B, Reovirus-1, Sindbis, Reovirus-1, Punta
Toro, human immunodeficiency virus type 1 strain IIIB, and human immun-
odeficiency virus type 2 strain ROD. The antiviral, other than anti-HIV, assays
were based on inhibition of virus-induced cytopathicity or plaque formation
in human embryonic lung (HEL) fibroblasts, African green monkey cells
(Vero), human epithelial cells (HeLa), or Madin-Darby canine kidney cells
(MDCK). Confluent cell cultures in microtiter 96-well plates were inoculated
with 100 CCID50 of virus (1 CCID50 being the virus dose to infect 50% of the
cell cultures) or with 20 plaque-forming units (PFU) (VZV) in the presence of
varying concentrations of the test compounds. Viral cytopathicity or plaque
formation was recorded as soon as it reached completion in the control virus-
infected cell cultures that were not treated with the test compounds. Antiviral
activity was expressed as the EC50 or compound concentration required
to reduce virus-induced cytopathogenicity or viral plaque formation by
50%.

Novel 5-arylcarbamoyl-2-methylisoxazolidin-3-yl-3-phosphonates
Anti-HIV Activity Assays
579
Inhibition of HIV-1(IIIB)- and HIV-2(ROD)-induced cytopathicity in
CEM cell cultures was measured in microtiter 96-well plates containing ∼
3 × 105 CEM cells/mL infected with 100 CCID50 of HIV per milliliter and
containing appropriate dilutions of the test compounds. After 4 to 5 days
of incubation at 37◦C in a CO2-controlled humidified atmosphere, CEM
giant (syncytium) cell formation was examined microscopically. The EC50
(50% effective concentration) was defined as the compound concentration
required to inhibit HIV-induced giant cell formation by 50%.
Cytostatic Activity Assays
All assays were performed in 96-well microtiter plates. To each well,
(5−7.5) × 104 tumor cells and a given amount of the test compound were
added. The cells were allowed to proliferate for 48 hours (murine leukemia
L1210 cells) or 72 hours (human lymphocytic CEM and human cervix carci-
noma HeLa cells) at 37◦C in a humidified CO2-controlled atmosphere. At the
end of the incubation period, the cells were counted in a Coulter counter.
The IC50 (50% inhibitory concentration) was defined as the concentration
of the compound that inhibited cell proliferation by 50%.
ACKNOWLEDGMENTS
The authors wish to express their gratitude to Mrs. Jolanta Płocka, Mrs.
Leentje Persoons, Mrs. Frieda De Meyer, Mrs. Leen Ingels, Mr. Steven Car-
mans, Mrs. Lies Van den Heurck, Mrs. Anita Camps, and Mrs. Lizette van
Berckelaer for excellent technical assistance. The synthetic part of this work
was supported by the Medical University of Ło´dz´ internal found (503/3-
014–1/503-01 and 502-03-/3-014-01/502-34-020). The biological part of this
work was supported by the KU Leuven (GOA 10/014).
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