Synthesis, anti-varicella-zoster virus and anti-cytomegalovirus activity of quinazoline-2,4-diones containing isoxazolidine and phosphonate substructures

Article abstract of DOI:10.1016/j.ejmech.2016.10.002

Cycloadditions of N-substituted C-(diethoxyphosphoryl)nitrones to N-allylated quinazoline-2,4-diones functionalized at N3 with substituted benzoyl or benzyl groups proceeded with moderate to good diastereoselectivities (d.e. 28–68%). The synthesized isoxazolidine phosphonates were assessed for the antiviral activity against a broad range of DNA and RNA viruses. Compounds trans-13c, cis-13c/trans-13c (86:14), cis-15b/trans-15b (87:13) and trans-15d/cis-15d (95:5) exhibited the highest activity toward both TK⁺and TK^?VZV strains (mean EC₅₀values in the range of 3.0–8.7?μM). The EC₅₀'s for isoxazolidines trans-12a, cis-12a, cis-13a, trans-13d, cis-15a/trans-15a (50:50) ranged between 6.9 and 8.5?μM for VZV TK⁺strain and between 10.7 and 13.2?μM for VZV TK^–strain. The isoxazolidine phosphonates cis-15/trans-15 having benzyl substituents both at N3 of the quinazoline-2,4-dione skeleton and at N2 of the isoxazolidine ring displayed some anti-cytomegalovirus potency but at the same time showed significant cytostatic activity for human embryonic lung fibroblasts (used to carry out the antiviral assays) as well as for other cell lines (i.e. CEM, L1210, HeLa and HMEC-1).

Full text of DOI:10.1016/j.ejmech.2016.10.002

Accepted Manuscript
Synthesis, anti-varicella-zoster virus and anti-cytomegalovirus activity of
quinazoline-2,4-diones containing isoxazolidine and phosphonate substructures
Dorota G. Piotrowska, Graciela Andrei, Dominique Schols, Robert Snoeck,
Magdalena Łysakowska
PII:
S0223-5234(16)30864-9
10.1016/j.ejmech.2016.10.002
EJMECH 8967
DOI:
Reference:
To appear in: European Journal of Medicinal Chemistry
Received Date: 27 July 2016
Revised Date: 29 September 2016
Accepted Date: 2 October 2016
Please cite this article as: D.G. Piotrowska, G. Andrei, D. Schols, R. Snoeck, M. Łysakowska, Synthesis,
anti-varicella-zoster virus and anti-cytomegalovirus activity of quinazoline-2,4-diones containing
isoxazolidine and phosphonate substructures, European Journal of Medicinal Chemistry (2016), doi:
10.1016/j.ejmech.2016.10.002.
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Graphical Abstract
Synthesis, anti-varicella-zoster virus and anti-cytomegalovirus activity of quinazoline-
2,4-diones containing isoxazolidine and phosphonate substructures
Dorota G. Piotrowska,* Graciela Andrei, Dominique Schols, Robert Snoeck and Magdalena
Łysakowska

ACCEPTED MANUSCRIPT
Synthesis, anti-varicella-zoster virus and anti-cytomegalovirus activity of quinazoline-
2,4-diones containing isoxazolidine and phosphonate substructures
Dorota G. Piotrowska,*,a Graciela Andrei,b Dominique Schols,b Robert Snoeckb and
Magdalena Łysakowskaa
a
Bioorganic Chemistry Laboratory, Faculty of Pharmacy, Medical University of Łódź, 90-151 Łódź,
Muszyńskiego 1, Poland
b Rega Institute for Medical Research, KU Leuven, Minderbroedersstraat 10, B-3000 Leuven, Belgium
Corresponding author. Tel: +48 42 677 92 35; fax:+48 42 678 83 98. E-mail address:
dorota.piotrowska@umed.lodz.pl
Keywords: phosphonates; isoxazolidines; quinazoline-2,4-diones; antiviral; cytostatic
Abstract
Cycloadditions of N-substituted C-(diethoxyphosphoryl)nitrones to N-allylated quinazoline-
2,4-diones functionalized at N3 with substituted benzoyl or benzyl groups proceeded with
moderate to good diastereoselectivities (d.e. 28–68%). The synthesized isoxazolidine
phosphonates were assessed for the antiviral activity against a broad range of DNA and RNA
viruses. Compounds trans-13c, cis-13c/trans-13c (86:14), cis-15b/trans-15b (87:13) and
trans-15d/cis-15d (95:5) exhibited the highest activity toward both TK+ and TK– VZV strains
(mean EC50 values in the range of 3.0–8.7 µM). The EC50’s for isoxazolidines trans-12a, cis-
12a, cis-13a, trans-13d, cis-15a/trans-15a (50:50) ranged between 6.9–8.5 µM for VZV TK+
strain and between 10.7–13.2 µM for VZV TK– strain. The isoxazolidine phosphonates cis-
15/trans-15 having benzyl substituents both at N3 of the quinazoline-2,4-dione skeleton and
at N2 of the isoxazolidine ring displayed some anti-cytomegalovirus potency but at the same
time showed significant cytostatic activity for human embryonic lung fibroblasts (used to

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carry out the antiviral assays) as well as for other cell lines (i.e. CEM, L1210, HeLa and
HMEC-1).
1. Introduction
Herpesviruses are widespread among humans and may cause many diseases. The primary
infection is usually followed by a life-long latency of the virus and its reactivation usually
occurs during immunosuppression of the host. Infection with varicella-zoster virus (VZV)
results in varicella (chickenpox) which usually takes a mild course in children but may be
more severe in adults. Later on, after establishing latency in neural tissues, the virus can
reactivate causing herpes zoster (shingles) which is often accompanied by neuralgic pain and
can lead to post-herpetic neuralgia (PHN) as well as other complications such as loss of vision
(zoster ophthalmicus) [1,2].
In most cases immunocompetent patients infected by herpesviruses do not require antiviral
therapy. However, reactivation of the virus is of significant concern in immunocompromised
individuals, e.g. recipients of solid-organ and hematopoietic stem cell transplant, patients
under aggressive chemotherapy or individuals with acquired immunodeficiency syndrome
(AIDS). Under these circumstances, efficient antiviral drugs are of crucial importance.
Effective treatments of herpesviridae species, including herpes simplex virus (HSV), VZV
and human cytomegalovirus (HCMV) [3,4] are available but they are hampered by emergence
of drug resistance and significant drug toxicities for some anti-herpesvirus agents (such as
ganciclovir, foscavir and cidofovir). Four compounds are currently licensed for the treatment
of VZV infections, namely acyclovir, valaciclovir, famciclovir and brivudin [5,6].
Regrettably, AIDS patients often do not respond well to acyclovir therapy or other antiviral
drugs due to the emergence of thymidine kinase-deficient or thymidine kinase-altered
mutations of VZV [7,8]. Therefore, the extensive search for new anti-VZV agents with
superior efficacy compared to currently approved drugs is of high importance.
Numerous structurally diversified compounds have already been synthesized and tested as
new potential anti-VZV agents including bicyclic nucleoside analogues, non-nucleoside DNA
polymerase inhibitors and N-(α-methylbenzyl)-N-arylthiourea analogues (Figure 1) [9–18].

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R
O
O
O
N
R
N
N
N
NH
Cl
N
HO
O
N
N
S
S
Cl
OH
R = Alkyl,R = 4-Alkyl-C6H4
O
H
H
N
R'
N
S
N
O
O
O
S
N
R
N
N
O
H
H
N
O
R = 4-F-C6H4, R' = 2-F-C6H4
R = benzofuran-2-yl, R' = isoquinoline-1-yl
O
O
O
N
O
N
N
N
N
H
H
O
O
N
Cl
Cl
R
Figure 1. Examples of anti-VZV active compounds.
On the other hand, the antiviral activity of several 1,3-disubstituted quinazoline-2,4-diones
(Figure 2) has been discovered in recent years [19]. A 3-benzylquinazolin-2,4-dione
derivative 1 was reported to posses the anti-HIV-1 activity in MT-4 cells and inhibited the
recombinant RT in vitro [20]. A quinazolinone-2,4-dione 2 was a potent inhibitor of RSV-
induced cytopathic effect (EC50 = 2.14 µM) [21]. Several other analogues, namely 3–5,
proved to be very active toward Respiratory Syncytial Virus (RSV) [21]. Recently, the N3-
benzoylquinazolinonedione moiety was successfully incorporated as a nucleobase mimetic
into the 1,2,3-triazole analogues of nucleotides 6 [22] and 7 [23]. While the compound 6
showed a moderate activity against both herpes simplex viruses (HSV-1 and HSV-2) (EC50 =
17 µM) as well as feline herpes virus (EC50 = 24 µM), its dihydroxylated derivative (1R,2S)-7
proved to be even more potent (EC50 = 2.9, 4 and 4 µM toward HSV-1, HSV-2 and feline
herpes virus, respectively), while the enantiomer (1S,2S)-16 was inactive [23]. From several

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functionalized quinazoline-2,4-diones studied as allosteric inhibitors of the NS5B polymerase
compounds 8–10 exhibited the highest affinity to the enzyme [24]. On the basis of these
observations one may conclude that for the antiviral activity of quinazoline-2,4-diones
substitution at N3 with aryl, benzyl or benzoyl groups is beneficial.
Figure 2. Examples quinazoline-2,4-dione derivatives exhibiting antiviral activity.
2. Results and Discussion
2.1. Chemistry
Recently, we successfully accomplished the syntheses of homonucleoside analogues 11 which
proved inactive against a broad spectrum of DNA and RNA viruses while some of them
appeared slightly cytostatic toward several cancerous cell lines [25]. However, later on they
were additionally screened for inhibition of VZV and HCMV replication and two compounds
11a (B = N-benzoyluracil) and 12a (R = benzoyl, R′ = methyl) showed noticeable activity
toward VZV (Table 3). Based on this discovery we designed a new series of analogues
(Scheme 1) installing at N3 of the quinazoline-2,4-dione skeleton either substituted benzoyl
groups (compounds 2 and 3) or substituted benzyl residues (compounds 14 and 15).

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Scheme 1. Retrosynthesis of quinazoline-2,4-diones 12–15.
As previously reported [25], N1-allyl-N3-benzoylquinazoline-2,4-dione 18a was obtained in
three steps in 20% overall yield starting from quinazoline-2,4-dione employing bis-N1,N3-
benzoylation with benzoyl chloride followed by the selective N1-debenzoylation and
subsequent allylation. However, this procedure appeared tedious and the N1-debenzylation
step was the least effective. For this reason another strategy for the syntheses of N1-allyl-N3-
benzoylquinazoline-2,4-diones 18a-18d was designed which relied on N-allylation of the
commercially available isatoic anhydride 20 followed by a subsequent condensation of
compound 21 with urea [26,27] and concluded with N3-benzoylation of the resulted N-
allylquinazoline-2,4-dione 22 with selected benzoyl chlorides (Scheme 2). Moreover, under
these circumstances compounds 19a-d could be obtained in one step by benzylation of
allylquinazoline-2,4-dione 22 (Scheme 2).
Scheme 2. Synthesis of quinazoline-2,4-diones 18a-d and 19a-d.

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1,3-Dipolar cycloadditions of nitrones 16 (R′ = Me) or 7 (R′ = Bn) with the respective N1-
allyl-N3-benzoylquinazoline-2,4-diones 18a-d were carried out at 60°C in toluene or toluene-
ethanol mixtures as solvents and afforded mixtures of diastereoisomeric isoxazolidines trans-
12 and cis-12 or trans-13 and cis-13 (Scheme 3, Table 1) with the trans-isomer
predominating. The cis/trans ratios of diastereoisomeric products were determined on the
basis of the 31P NMR spectral data. The reactions proceeded with moderate
diastereoselectivities (d.e. 28–60%) and with good to excellent overall yields. The isolation of
pure isomers was successfully accomplished chromatographically for major isomers trans-
12a, trans-12b, trans-12c, trans-12d, trans-13c and trans-13d but also for minor isomers cis-
12a, cis-12d and cis-13a.
Scheme 3. Reaction and conditions: a) toluene or toluene-ethanol, 60°C, 72 h.
Table 1. Cycloadditions of the nitrone 16/17 and N1-allyl-N3-benzoylquinazoline-2,4-diones 18a-d.
Nitrone
Alkene 18 (R)
cis : trans
Yield (%)
ratio
16/17 (R′)
16 (Me)17
16 (Me)
16 (Me)
16 (Me)
17 (Bn)
17 (Bn)
18a (Ph) [25]
18b (2-F-C6H4)
18c (3-F-C6H4)
18d (4-F-C6H4)
18a (Ph)
20:80
36:64
20:80
25:75
27:73
32:68
cis-12a (11)a, trans-12a (43)a, cis-12a + trans-12a (25)b
trans-12b (43)a, cis-12b + trans-12b (49)b
trans-12c (47)a, cis-12c + trans-12c (46)b
cis-12d (4.5)a, trans-12d (25)a, cis-12d +trans-12d (53)b
cis-13a (7.1)a, trans-13a (3.6)a, cis-13a + trans-13a (74)b
cis-13b + trans-13b (92)b
18b (2-F-C6H4)

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17 (Bn)
17 (Bn)
18c (3-F-C6H4)
18d (4-F-C6H4)
28:72
trans-13c (13)a, cis-13c + trans-13c (81)b
trans-13d (27)a, cis-13d + trans-13d (61)b
28:72
a) Yield of the pure isomer.
b) Yield of the pure mixture of cis- and trans-isomers.
To eliminate rigidity within the substituted quinazoline-2,4-dione moiety benzoyl substituents
at N3 were replaced by the functionalized benzyl residues. 1,3-Dipolar cycloadditions of
nitrones 16 (R′ = Me) or 7 (R′ = Bn) with the respective N1-allyl-N3-benzylquinazoline-2,4-
diones 19a-d were carried out under conditions already described for compounds 18.
Diastereoisomeric cycloadducts trans-14 and cis-14 or trans-15 and cis-15 (Scheme 3, Table
2) were formed in good to excellent overall yields and with moderate diastereoselectivities
(d.e. 28–60%) which were slightly higher for reactions of the nitrone 7 (R′ = Bn).
Chromatographic isolation of pure isomers was achieved for trans-14a, cis-14b, trans-14b,
trans-14c and trans-14d.
Scheme 4. Reaction and conditions: a) toluene or toluene-ethanol, 60°C, 72h.
Table 2. Cycloadditions of the nitrones 16 or 17 and N1-allyl-N3-benzylquinazoline-2,4-diones 19a-d.
Nitrone
Alkene 19 (R)
cis : trans
Yield (%)
ratio
16/17 (R′)
16 (Me)
16 (Me)
16 (Me)
19a (Ph)
22:78
22:78
16:84
trans-14a (37)a, cis-14a + trans-14a (58)b
cis-14b (6.5)a, trans-14b (29)a, cis-14b + trans-14b (56)b
trans-14c (21)a, cis-14c + trans-14c (75)b
19b (2-F-C6H4)
19c (3-F-C6H4)

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16 (Me)
17 (Bn)
17 (Bn)
17 (Bn)
17 (Bn)
19d (4-F-C6H4)
19a (Ph)
23:77
34:66
31:69
35:65
33:67
trans-14d (30)a, cis-14d + trans-14d (56)b
cis-15a +trans-15a (92)b
cis-15b (3.6)a, cis-15b +trans-15b (86)b
cis-15c +trans-15c (96)b
19b (2-F-C6H4)
19c (3-F-C6H4)
19d (4-F-C6H4)
cis-15d +trans-15d (95)b
a) Yield of the pure isomer.
b) Yield of the pure mixture of cis- and trans-isomers.
2.2. Antiviral and cytostatic evaluation
The pure isomers of quinazoline-2,4-dione - conjugates [trans-11a, cis-11a, trans-12a, cis-
12a, trans-13a, cis-13a, trans-12b, trans-12c, trans-13c, trans-12d, cis-12d, trans-13d, trans-
14a, trans-14b, cis-14b, trans-15b, trans-14c, trans-14d] and the respective mixtures of
cis/trans isomers [cis-12b/trans-12b (87:13), trans-13b/cis-13b (90:10), cis-2c/trans-2c
(94:6), cis-13c/trans-13c (86:14), cis-13d/trans-13d (85:15), cis-14a/trans-14a (75:25), trans-
15a/cis-15a (90:10), cis-15a/trans-15a (50:50), cis-15b/trans-15b (87:13), cis-14c/trans-14c
(97:3), trans-15c/cis-15c (90:10), cis-15c/trans-15c (80:20), cis-14d/trans-14d (75:25), trans-
15d/cis-15d (95:5), cis-15d/trans-15d (75:52)] were screened as inhibitors of a wide variety
of DNA and RNA viruses using the following cell-based assays: (a) human embryonic lung
(HEL) cells: herpes simplex virus-1 (KOS strain), herpes simplex virus-2 (G strain),
thymidine kinase deficient (acyclovir resistant) herpes simplex virus-1 (TK– KOS ACVr
strain), vaccinia virus, adenovirus-2, vesicular stomatitis virus, human coronavirus (229E),
cytomegalovirus (AD-169 strain and Davis strain), varicella-zoster virus (TK+ VZV Oka
strain and TK– VZV 07-1 strain); (b) HeLa cell cultures: vesicular stomatitis virus, Coxsackie
virus B4 and respiratory syncytial virus; (c) Vero cell cultures: parainfluenza virus 3,
reovirus-1, Sindbis virus, Coxsackie virus B4, Punta Toro virus, yellow fever virus; (e)
Crandell-Rees feline kidney (CRFK) cell cultures: feline corona virus (FIPV) and feline
herpes virus (FHV) and (d) Madin Darby canine kidney (MDCK) cell cultures: influenza A
virus (H1N1 and H3N2 subtypes) and influenza B virus. Ganciclovir, cidofovir, acyclovir,
brivudin, zalcitabine, zanamivir, alovudine, amantadine, rimantadine, ribavirin, dextran
sulfate (molecular weight 10000, DS-10000), mycophenolic acid, Hippeastrum hybrid

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agglutinin (HHA) and Urtica dioica agglutinin (UDA) were used as the reference compounds.
The antiviral activity was expressed as the EC50: the compound concentration required to
reduce virus plaque formation (VZV) by 50% or to reduce virus-induced cytopathogenicity by
50% (other viruses).
Several synthesized quinazoline-2,4-diones inhibited the replication of both TK+ and TK–
VZV strains (Table 3). A 95:5 trans-15d/cis-15d mixture and a 87:13 cis-15b/trans-15b
mixture emerged as the most active derivatives with EC50’s of, respectively, 4.7 µM and 3 µM
(VZV TK+ strain) and of 3.6 µM and 5.1 µM (VZV TK– strain). These two quinazoline-2,4-
diones were 4 to 6-fold less active against the TK+ virus but proved to be 10 to 14-fold more
active against the TK– strain when compared to the reference drug acyclovir. These data
clearly indicate that these novel derivatives do not require activation by the viral TK.
Although these quinazoline-2,4-diones did not significantly altered the morphology of cells in
the antiviral assays, they showed considerable cytostatic activity (in the same range as the
antiviral activity).
Compounds trans-13c, a 86:14 cis-13c/trans-13c mixture, trans-13d, and a 85:15 cis-
13d/trans-13d mixture inhibited both VZV TK+ and TK– viruses with EC50’s in the range of
6.0–8.5 µM. Compounds trans-12a, cis-12a, cis-13a, trans-12d and a 50:50 cis-15a/trans-15a
mixture also proved active against VZV TK+ strain (EC50’s of 6.9–7.5 µM) and VZV TK–
strain (EC50’s of 10-14 µM), slightly exceeding in potency against VZV TK– strains the
reference drugs acyclovir and brivudin (EC50 = 50.3 µM and 22.7, respectively). However,
majority of the studied compounds exhibited significant cytotoxicity and the 95:5 trans-
15d/cis-15d mixture reduced cell growth (CC50) at concentration as low as 6.6 µM which was
almost two orders of magnitude lower than that for acyclovir (CC50 = 440 µM).
Table 3. Antiviral activity and cytotoxicity against varicella-zoster virus (VZV) in HEL cell cultures.
Antiviral activity EC50 (µM)a
Cytotoxicity (µM)
TK+ VZV
strain
TK– VZV
strain
Compound
trans-11a
R′
Me
R
Cell morphology
(MCC)b
Cell growth
(CC50)c
83.6
> 100
> 100
> 100
n.d.
n.d.
cis-11a
trans-12a
Me
Me
Me
Bn
65.7
88.4
13.7 ± 4.7
10.9 ± 1.6
> 20 ± 0
10.8 ± 1.7
34.2
C6H5
C6H5
C6H5
C6H5
7.5 ± 2.1d
7.7 ± 2.4
8.5 ± 3.8
8.5 ± 0.3
36.57
≥100 ± 0
> 100 ± 0
100 ± 0
100 ± 0
> 100
> 100 ± 0
> 100 ± 0
28.9 ± 3.1
16.34 ± 0
n.d.
cis-12a
trans-13a
cis-13a
Bn
trans-12b
Me
Me
Bn
2-F-C6H4
2-F-C6H4
2-F-C6H4
3-F-C6H4
3-F-C6H4
cis-12b/trans-12b (87:13)
trans-13b/cis-13b (90:10)
trans-12c
28.99
25.62
> 100
n.d.
16.7 ± 4.7
16.7 ± 4.7
7.8 ± 3.6
20 ± 0
100 ± 0
> 100 ± 0
> 100 ± 0
21.4 ± 1.0
16.5 ± 2.5
30.0 ± 11.2
Me
Me
15.0 ± 3.3
21.4 ± 13.0
cis-12c/trans-12c (94:6)

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trans-13c
cis-13c/trans-13c (86:14)
trans-12d
Bn
Bn
Me
Me
Bn
Bn
Me
Me
Bn
Bn
Me
Me
Bn
Bn
Me
Me
Bn
Bn
Me
Me
Bn
Bn
3-F-C6H4
3-F-C6H4
4-F-C6H4
4-F-C6H4
4-F-C6H4
4-F-C6H4
C6H5
8.7 ± 4.3
6.0 ± 6.9
6.9 ± 5.3
26.15
8.5 ± 4.6
8.5 ± 9.6
10.7 ± 0.3
24.46
100 ± 0
100 ± 0
≥100 ± 0
> 100
100 ± 0
100 ± 0
100
9.8 ± 2.3
19.3 ± 5.3
14.7 ± 2.1
n.d.
cis-12d
trans-13d
7.5 ± 0.1
7.4 ± 0.8
> 20
8.3 ± 0.2
7.6 ± 1.1
> 20
12.7 ± 2.7
12.3 ± 2.0
n.d.
cis-13d/trans-13d (85:15)
trans-14a
cis-14a/trans-14a (75:25)
trans-15a/cis-15a (90:10)
cis-15a/trans-15a (50:50)
trans-14b
C6H5
> 100
> 100
> 100
100
n.d.
C6H5
> 20
> 20
n.d.
C6H5
7.3 ± 1.0
> 20
13.2 ± 9.7
> 20
100 ± 0
100
9.0 ± 0.7
n.d.
2-F-C6H4
2-F-C6H4
2-F-C6H4
2-F-C6H4
3-F-C6H4
3-F-C6H4
3-F-C6H4
3-F-C6H4
4-F-C6H4
4-F-C6H4
4-F-C6H4
4-F-C6H4
cis-14b
58.48
> 100
> 100
20
n.d.
trans-15b
4
> 20
n.d.
cis-15b/trans-15b (87:13)
trans-14c
4.7 ± 3.8
55.7
5.1 ± 1.6
> 100
100 ± 0
> 100
≥100 ± 0
100
11.8 ± 4.6
n.d.
cis-14c/trans-14c (97:3)
trans-15c/cis-15c (90:10)
cis-15c/trans-15c (80:20)
trans-14d
7.0 ± 1.4
> 20
27.1 ± 10.0
20
36.8 ± 3.1
n.d.
> 20
> 20
100
n.d.
66.87
> 20
10
n.d.
cis-14d/trans-14d (75:25)
trans-15d/cis-15d (95:5)
cis-15d/trans-15d (75:52)
35.54
25.17
100
n.d.
3.0 ± 2.3
> 4
3.6 ± 2.9
> 4
100 ± 0
20
6.6 ± 0
n.d.
0.8 ± 0.1
0.005± 0.007
50.3 ± 14.9
22.7 ± 3.1
> 440 ± 0
> 300 ± 0
440 ± 0
300 ± 0
Acyclovir
Brivudin
a Effective concentration required to reduce virus plaque formation by 50%. Virus input was 100 plaque forming units (PFU),
b Minimum cytotoxic concentration that causes a microscopically detectable alternation of cell morphology,
c Cytotoxic concentration required to reduce cell growth by 50%,
d Results are mean values ± STDEV of two independent experiments,
n.d. – not determined,
Among the investigated quinazoline-2,4-diones, the N3-benzoylated compounds (cis- and
trans-12/13) were found inactive toward both human cytomegalovirus (HCMV) strains. On
the other hand, isoxazolidine phosphonates having benzyl substituents both at N3 of the
quinazoline-2,4-dione skeleton and at N2 of the isoxazolidine ring (cis- and trans-15) showed
weak antiviral activity with EC50 in the range of ≥3 to ≥14.5 µM (Table 4).
Preliminary structure-activity relationship observations revealed a lack of significant
differences in activity of cis vs. trans isoxazolidines and higher potency of isoxazolidines
carrying N-benzyl substituents in comparison with their N-methyl counterparts especially
well pronounced for the N3-benzylquinazoline-2,4-diones 15. For the active compounds the
introduction of a fluorine atom into the benzene ring either in benzyl or benzoyl residues did
not improve their efficacy. While the quinazoline-2,4-diones substituted at N3 with benzoyl
and benzyl moieties were found effective against VZV, only those carrying substituted benzyl
components proved active toward HMCV.
Table 4. Antiviral activity and cytotoxicity against human cytomegalovirus in HEL cell cultures.

ACCEPTED MANUSCRIPT
Antiviral activity EC50 (µM)a
Cytotoxicity (µM)
Compound
trans-11a
R′
Me
R
AD-169 strain
Davis strain
Cell morphology
Cell growth
(CC50)c
n.d.
(MCC)b
100
> 100
> 100
> 100
> 100
> 20
> 100
> 100
> 100
> 100
> 20
cis-11a
trans-12a
Me
Me
Me
Bn
Bn
Me
Me
Bn
Me
Me
Bn
Bn
Me
Me
Bn
Bn
Me
Me
Bn
Bn
Me
Me
Bn
Bn
Me
Me
Bn
Bn
Me
Me
Bn
Bn
100
100
n.d.
n.d.
C6H5
C6H5
C6H5
C6H5
cis-12a
100
n.d
trans-13a
100
n.d.
cis-13a
> 20
> 20
100
n.d.
trans-12b
2-F-C6H4
2-F-C6H4
2-F-C6H4
3-F-C6H4
3-F-C6H4
3-F-C6H4
3-F-C6H4
4-F-C6H4
4-F-C6H4
4-F-C6H4
4-F-C6H4
C6H5
> 20
66.87
63.14
> 20
100
n.d.
cis-12b/trans-12b (87:13)
trans-13b/cis-13b (90:10)
trans-12c
> 100
> 20
100
n.d.
100
n.d.
> 20
> 20
100
n.d
cis-12c/trans-12c (94:6)
trans-13c
> 100
> 20
> 100
> 20
100
n.d.
20
n.d.
cis-13c/trans-13c (86:14)
trans-12d
> 20
> 20
100
n.d.
> 20
> 20
100
n.d.
cis-12d
> 20
> 20
100
n.d.
trans-13d
> 20
> 20
20
n.d
cis-13d/trans-13d (85:15)
trans-14a
> 20
> 20
20
n.d.
> 100
> 100
≥14.5 ± 7.8d
≥3.0 ± 1.4
> 100
> 100
> 20
> 100
> 100
13.1 ± 3.1
6.5 ± 3.5
100
100
n.d
cis-14a/trans-14a (75:25)
trans-15a/cis-15a (90:10)
cis-15a/trans-15a (50:50)
trans-14b
C6H5
100
n.d.
C6H5
100 ± 0
100 ± 0
20
41.7 ± 10.8
9.0 ± 0.7
n.d.
C6H5
2-F-C6H4
2-F-C6H4
2-F-C6H4
2-F-C6H4
3-F-C6H4
3-F-C6H4
3-F-C6H4
3-F-C6H4
4-F-C6H4
4-F-C6H4
4-F-C6H4
4-F-C6H4
cis-14b
100
100
n.d.
trans-15b
> 4
20
n.d
cis-15b/trans-15b (87:13)
trans-14c
8.94 ± 0
76.47
> 20
≥6.5 ± 3.5
63.14
44.72
8.94 ± 1
> 20
100 ± 1
> 100
100
11.8 ± 4.6
n.d.
cis-14c/trans-14c (97:3)
trans-15c/cis-15c (90:10)
cis-15c/trans-15c (80:20)
trans-14d
n.d.
9.9 ± 1.4
> 20
100 ± 0
20
20.8 ± 4.7
n.d.
> 100
> 20
100
100
n.d.
cis-14d/trans-14d (75:25)
trans-15d/cis-15d (95:5)
cis-15d/trans-15d (75:52)
Ganciclovir
> 20
100
n.d.
≥6.5 ± 3.5
> 4
8.94 ± 0
> 4
100 ± 0
20
6.6 ± 0
n.d.
14.9 ± 8.1
6.5 ± 2.5
> 350 ± 0
> 350 ± 0
Cidofovir
1.44 ± 0.56
0.81 ± 0.07
> 300 ± 0
> 300 ± 0
a Effective concentration required to reduce virus plaque formation by 50%. Virus input was 100 plaque forming units (PFU),
b Minimum cytotoxic concentration that causes a microscopically detectable alternation of cell morphology,
c Cytotoxic concentration required to reduce cell growth by 50%,
d Results are mean values ± STDEV of two independent experiments,
n.d. – not determined,
All synthesized isoxazolidine phosphonates were also subjected to antiviral screening with
other viruses, but only compound trans-12d appeared slightly active against other
herpesviruses, adenovirus-2 and human Coronavirus (Table 5).
Table 5. Antiviral activity and cytotoxicity in HEL cell cultures.
Antiviral activity EC50 (µM)b
Minimum
cytotoxic
Herpes
simplex
virus-1
Herpes
simplex
virus-2
Herpes
simplex
Adeno
virus-2
Human
Coronavirus
(229E)
Compound
R′
R
concentration
(µM)a
virus-1 TK–

ACCEPTED MANUSCRIPT
(KOS)
(G)
12.0 ± 0
KOS ACVr
9.0 ± 1.4
trans-12d
Brivudine
Cidofovir
Acyclovir
Ganciclovir
Zalcitabine
Alovudine
UDA
Me
4-F-C6H4
39.0 ± 15.6c
17.5 ± 3.5
39.5 ± 7.8
≥ 100 ± 0
> 250
> 250
> 250
> 100
> 250
> 250
≥ 100
≥ 250
0.11
146
250
-
10
-
-
2
2
3.8
-
-
0.2
0.4
250
0.032
0.055
4
-
-
-
-
-
-
-
-
-
-
-
7.2
10
-
-
-
-
-
0.4
112
Ribavirin
-
-
a Requird to cause a microscopically detectable alteration of normal cell morphology,
b Required to reduce virus-induced cytopathogenicity by 50%,
c Results are mean values ± STDEV of two independent experiments,
2.3. Cytostatic activity
The 50% cytostatic inhibitory concentration (IC50) causing a 50% decrease in cell
proliferation was determined against murine leukemia L1210, human lymphocyte CEM,
human cervix carcinoma HeLa and immortalized human dermal microvacsular endothelial
cells (HMEC-1) (Table 6). Among all tested compounds only quinazoline-2,4-diones trans-
15/cis-15 having benzyl substituents at N3 in the quinazolinone core and the benzyl group at
N2 of the isoxazolidine unit showed significant cytostatic activity toward the tested cell lines.
For the CEM cell line, these derivatives were as active as the reference drug 5-fluorouracil. It
was noticed that the replacement of the benzyl component within the isoxazolidine moiety for
the methyl group (trans-15/cis-15 vs. the respective trans-14/cis-14) resulted in decrease in
potency by roughly an order of magnitude.
Table 6. The inhibitory effect of the tested compounds against the proliferation of murine leukemia (L1210),
human T-lymphocyte (CEM), human cervix carcinoma (HeLa) and immortalized human dermal microvascular
endothelial cells (HMEC-1).
IC50a (µM)
Compound
trans-11a [25]
R′
Me
R
L1210
> 200
CEM
> 200
HeLa
> 200
> 200
96 ± 11
> 200
> 250
> 250
> 250
> 250
> 250
> 250
> 250
HMEC-1
n.d b
cis-11a [25]
trans-12a [25]
cis-12a [25]
trans-13a
Me
Me
Me
Bn
Bn
Me
Me
Bn
Bn
Me
> 200
> 200
n.d
C6H5
C6H5
≥ 159
70 ± 22c
74 ± 33
≥ 250
n.d.
> 200
n.d.
C6H5
154 ± 54
155 ± 61
> 250
> 250
> 250
> 250
> 250
≥ 250
≥ 250
> 250
cis-13a
C6H5
≥ 250
trans-12d
4-F-C6H4
4-F-C6H4
4-F-C6H4
4-F-C6H4
2-F-C6H4
> 250
cis-12d
> 250
> 250
trans-13d
123 ± 40
105 ± 46
> 250
170 ± 22
132 ± 45
> 250
cis-13d/trans-13d (85:15)
trans-12b

ACCEPTED MANUSCRIPT
cis-12b/trans-12b (87:13)
trans-13b/cis-13b (90:10)
trans-12c
Me
Bn
Me
Me
Bn
Bn
Me
Me
Bn
Bn
Me
Me
Bn
Bn
Me
Me
Bn
Bn
Me
Me
Bn
Bn
2-F-C6H4
2-F-C6H4
3-F-C6H4
3-F-C6H4
3-F-C6H4
3-F-C6H4
C6H5
> 250
155 ± 79
228 ± 30
> 250
> 250
158 ± 13
> 250
> 250
≥ 250
> 250
> 250
> 250
> 250
cis-12c/trans-12c (94:6)
trans-13c
> 250
> 250
> 250
170 ± 105
185 ± 89
141 ± 28
146 ± 1
17 ± 7
224 ± 37
166 ± 118
124 ± 9
104 ± 19
15 ± 4
> 250
> 250
cis-13c/trans-13c (86:14)
trans-14a
> 250
> 250
119 ± 18
95 ± 41
73 ± 9
235 ± 22
222 ± 39
28 ± 3
28 ± 1
189 ± 38
≥ 250
cis-14a/trans-14a (75:25)
trans-15a/cis-15a (90:10)
cis-15a/trans-15a (50:50)
trans-14b
C6H5
C6H5
C6H5
18 ± 1
10 ± 6
33 ± 21
74 ± 28
128 ± 40
79 ± 4
2-F-C6H4
2-F-C6H4
2-F-C6H4
2-F-C6H4
3-F-C6H4
3-F-C6H4
3-F-C6H4
3-F-C6H4
4-F-C6H4
4-F-C6H4
4-F-C6H4
4-F-C6H4
196 ± 74
203 ± 8
68 ± 4
99 ± 8
cis-14b
181 ± 20
98 ± 4
trans-15b
145 ± 1
23 ± 9
152 ± 1
149 ± 1
28 ± 4
204 ± 66
158 ± 8
≥ 250
cis-15b/trans-15b (87:13)
trans-14c
17 ± 1
20 ± 3
17 ± 0
132 ± 5
118 ± 8
17 ± 5
100 ± 16
77 ± 20
17 ± 2
88 ± 9
cis-14c/trans-14c (97:3)
trans-15c/cis-15c (90:10)
cis-15c/trans-15c (80:20)
trans-14d
86 ± 13
63 ± 18
73 ± 11
82 ± 16
158 ± 44
18 ± 1
89 ± 9
49 ± 12
93 ± 10
173 ± 51
13 ± 1
126 ± 6
≥ 250
cis-14d/trans-14d (75:25)
trans-15d/cis-15d (95:5)
cis-15d/trans-15d (75:52)
5-Fluorouracil
17 ± 0
26 ± 2
27 ± 1
n.d.
19 ± 0
17 ± 3
17 ± 1
0.33 ± 0.17
18 ± 5
0.54 ± 0.12
a 50% Inhibitory concentration or compound concentration required to inhibit tumor cell proliferation by 50%,
n.d. – not determined
c Results are mean values ± STDEV of two independent experiments,
3. Conclusions
Several
series
of
{5-(2,4-dioxo-3,4-dihydroquinazolin-1(2H)-yl)methyl]-2-
methylisoxazolidin-3-yl})phosphonates (cis-12/trans-12 and cis-14/trans-14) and {5-(2,4-
dioxo-3,4-dihydroquinazolin-1(2H)-yl)methyl]-2-benzylisoxazolidin-3-yl})phosphonates (cis-
13/trans-13 and cis-15/trans-15) modified at N3 in the quinazoline-2,4-dione moiety have
been
obtained
by
the
1,3-dipolar
cycloaddition
of
N-substituted
(C-
diethoxyphosphoryl)nitrones 16 (R=Me) and 17 (R=Bn) and the respective N1-allylated
quinazoline-2,4-diones substituted at N3 with benzoyl (compounds 18) or benzyl groups
(compounds 19).
The synthesized isoxazolidine phosphonates were evaluated against a variety of DNA and
RNA viruses and several derivatives appeared to be active against varicella-zoster virus and
human cytomegalovirus. Among all tested compounds, a 95:5 trans-15d/cis-15d (95:5) (EC50

ACCEPTED MANUSCRIPT
= 3.0 µM) and a cis-15b/trans-15b (87:13) (EC50 = 4.7 µM) showed the highest activity
toward TK+ VZV strain. The potency of these derivatives was 4-6 fold lower than that of
acyclovir, used as reference drug.
On the other hand, compounds trans-13c, mixture cis-13c/trans-13c (86:14), trans-13d, and a
85:15 mixture of cis-13d/trans-13d exhibited potency not only against TK+ VZV strain but
also toward TK– VZV strain and their anti-TK– VZV activity was significantly higher than
that of the reference drugs acyclovir and brivudin (EC50 = 50.3 and 22.7 µM, respectively).
The isoxazolidine phosphonates cis-15a-d/trans-15a-d having benzyl substituents both at N3
of the quinazoline-2,4-dione skeleton and at N2 of the isoxazolidine ring (cis- and trans-5)
showed some activity toward human cytomegalovirus (EC50 in the range of ≥3 to ≥14.5 µM).
The quinazoline-2,4-diones endowed with anti-VZV and anti-HCMV activity did not alter the
morphology of cells used in the antiviral assays up to a concentration of 100 µM. However,
these derivatives showed considerable cytostatic activity. Cytostatic activity of the obtained
compounds was also evaluated on L1210, CEM, HeLa and HMEC-1 cells. Among all tested
compounds, only quinazoline-2,4-diones (trans-15/cis-15) bearing benzyl substituents at N3
in the quinazolinone core and the benzyl group at N2 of the isoxazolidine unit showed
significant (IC50 = 10–98 µM) activity toward tested cell lines.
4. Experimental
4.1. General
13
31
1H, C and P NMR spectra were taken in CDCl3 on the Bruker Avance III spectrometers
(600 MHz) with TMS as internal standard at 600, 151 and 243 MHz, respectively.
IR spectra were measured on an Infinity MI-60 FT-IR spectrometer. Melting points were
determined on a Boetius apparatus and are uncorrected. Elemental 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.
N-methyl- and N-benzyl-C-(diethoxyphosphoryl)nitrones 16 and 17 were obtained according
to the literature procedures [28].

ACCEPTED MANUSCRIPT
4.2. Synthesis of 1-allylquinazoline-2,4-dione (22)
To a solution of 1-allyl-1H-benzo[d][1,3]oxazine-2,4-dione 21 (0.500 g, 2.46 mmol) in DMF
(10 mL) urea (0.221 g, 3.69 mmol) was added. The reaction mixture was stirred for 5 h, the
solvent was removed in vacuo and the residue was crystallized from ethanol to give pure 22
as a yellowish amorphous solid, m.p. = 218–219°C.
IR (KBr, cm–1) νmax: 3165, 3031, 2926, 1673, 1605, 1502, 1398, 1295, 921, 763, 752, 503. 1H
NMR (600 MHz, CDCl3): δ = 8.57 (bs, 1H, NH), 8.26–8.24 (m, 1H), 7.71–7.68 (m, 1H),
7.31–7.28 (m, 1H), 7.23–7.22 (m, 1H), 5.95 (ddt, 3J = 17.3 Hz, 3J = 10.1 Hz, 3J = 5.0 Hz, 1H,
4
2
CH2–CH=CH2), 5.31 (ddt, 3J = 10.1 Hz, J = 3.5 Hz, J = 0.7 Hz, 1H, CH2–CH=CHH), 5.26
(d, 3J = 17.3 Hz, 4J = 3.5 Hz, 2J = 0.7 Hz, 1H, CH2–CH=CHH), 4.79 (dt, 3J = 5.0 Hz, 4J = 3.5
Hz, 2H, CH2–CH=CH2); 13C NMR (150 MHz, CDCl3): δ = 161.60 (C=O), 149.97 (C=O),
141.06, 135.45, 131.05, 128.79, 123.21, 117.81, 116.03, 114.68, 45.15. Anal. calcd. For
C11H10N2O3: C, 65.34; H, 4.98; N, 13.85. Found: C, 65.11; H, 4.74; N, 13.83.
4.3. The benzoylation of N-allylquinazoline-2,4-dione 22 – the general procedure
To a solution of N-allylquinazoline-2,4-dione 22 (1.00 mmol) in acetonitrile (10 mL)
triethylamine was added (3.00 mmol) followed by the respective benzoyl chloride (2.20
mmol). The mixture was stirred at room temperature for 72 h. The solvent was removed in
vacuo, the residue was dissolved in methylene chloride (10 mL) and washed with water (3 ×
10 mL). The organic layer was dried (MgSO4), concentrated and purified by column
chromatography with methylene chloride-hexane mixture (7:3, v/v) and the appropriate
fractions were crystallized from a chloroform-hexane mixture.
4.3.1. 1-Allyl-3-(2-fluoro)benzoyl-1H-quinazoline-2,4-dione (18b)
An amorphous solid, m.p. = 141–142°C. IR (KBr, cm–1) νmax: 3253, 2923, 1739, 1693, 1658,
1
1608, 1478, 1454, 1172, 1013, 944, 755. H NMR (600 MHz, CDCl3): δ = 8.25 (dd, J = 7.9
Hz, J = 1.6 Hz, 1H), 8.15 (dt, J = 7,9 Hz, J = 1.7 Hz, 1H), 7.73 (ddd, J = 8.6 Hz, J = 7.3 Hz, J
= 1.6 Hz, 1H), 7.66–7.62 (m, 1H), 7.35 – 7.29 (m, 2H), 7.26 (d, J = 8.5 Hz, 1H), 7.12 (ddd, J
= 11.7 Hz, J = 8.3 Hz, J = 1.0 Hz, 1H), 5.95 (ddt, 3J = 17.2 Hz, 3J = 10.2 Hz, 3J = 4.9 Hz, 1H,

ACCEPTED MANUSCRIPT
CH2–CH=CH2), 5.32 (d, 3J = 10.2 Hz, 1H, CH2–CH=CHH), 5.28 (d, 3J = 17.2 Hz, 1H, CH2–
13
CH=CHH), 4.82–4.79 (m, 2H); C NMR (150 MHz, CDCl3): δ = 164.80 (C=O), 162.09 (d,
3
1J(CF) = 259.0 Hz), 160.79 (C=O), 149.07 (C=O), 140.41, 136.84 (d, J(CCCF) = 9.8 Hz),
135.85, 133.03, 130.73, 128.92, 125.03 (d, 4J(CCCCF) = 3.3 Hz), 123.43, 120.51 (d, 2J(CCF) = 7.8
2
Hz), 117.88, 117.21 (d, J(CCF) = 23.2 Hz), 114.84, 45.22. Anal. calcd. For C18H13FN2O3: C,
66.66; H, 4.04; N, 8.64. Found: C, 66.41; H, 3.73; N, 8.59.
4.3.2. 1-Allyl-3-(3-fluoro)benzoyl-1H-quinazoline-2,4-dione (18c)
An amorphous solid, m.p. = 125–127°C. IR (KBr, cm–1) νmax: 3073, 2973, 1743, 1697, 1670,
1
1481, 1432, 1286, 1048, 779. H NMR (600 MHz, CDCl3): δ = 8.25 (d, J = 7.9 Hz), 7.81–
7.75 (m, 2H), 7.67 (d, J = 8.8 Hz, 1H), 7.50 (dt, J = 8.0 Hz, J = 5.7 Hz, 1H), 7.38 (dt, J = 8.2
3
3
3
Hz, J = 2.1 Hz, 1H), 7.35–7.28 (m, 2H), 5.96 (ddt, J = 17.7 Hz, J = 10.9 Hz, J = 5.0 Hz,
3
3
1H, CH2–CH=CH2), 5.35 (d, J = 10.9 Hz, 1H, CH2–CH=CHH), 5.30 (d, J = 17.7 Hz, 1H,
CH2–CH=CHH), 4.80 (d, 3J = 5.0 Hz, 2H, CH2–CH=CH2); 13C NMR (150 MHz, CDCl3): δ =
1
167.72 (d, 4J(C(O)CCCF) = 3.2 Hz, C=O), 162.93 (d, J(CF) = 248.9 Hz), 161.03 (C=O), 149.13
3
3
(C=O), 140.49, 136.03, 133.99 (d, J(CCCF) = 7.3 Hz), 130.89 (d, J(CCCF) = 7.7 Hz), 130.77,
129.09, 126.14 (d, 4J(CCCCF) = 2.8 Hz), 122.10 (d, 2J(CCF) = 21.8 Hz), 118.39, 117.38 (d, 2J(CCF)
= 23.3 Hz), 115.59, 114.83, 45.44. Anal. calcd. For C18H13FN2O3: C, 66.66; H, 4.04; N, 8.64.
Found: C, 66,63; H, 3.64; N, 8.82.
4.3.3.1-Allyl-3-(4-fluoro)benzoyl-1H-quinazoline-2,4-dione (18d)
An amorphous solid, m.p. = 117.0–118.5°C. IR (KBr, cm–1) νmax: 3084, 2987, 1744, 1700,
1661, 1495, 1411, 1242, 994, 757. 1H NMR (600 MHz, CDCl3): δ = 8.27 (dd, J = 7.9 Hz, J =
1.5 Hz, 1H), 8.04–8.02 (m, 2H), 7.76 (ddd, J = 8.7 Hz, J = 7.6 Hz, J = 1.6 Hz, 1H), 7.34 (dd,
J = 7.7 Hz, J = 7.4 Hz, 1H), 7.30 (d, J = 8.5 Hz, 1H), 7.21–7.18 (m, 2H), 5.97 (ddt, 3J = 17.0
3
3
3
Hz, J = 10.7 Hz, J = 5.2 Hz, 1H, CH2–CH=CH2), 5.35 (d, J = 10.7 Hz, 1H, CH2–
3
3
CH=CHH), 5.30 (d, J = 17.0 Hz, 1H, CH2–CH=CHH), 4.81 (d, J = 5.2 Hz, 2H, CH2–
13
1
CH=CH2); C NMR (150 MHz, CDCl3): δ = 167.45 (C=O), 166.92 (d, J(CF) = 258.4 Hz),
3
161.06 (C=O), 149.17 (C=O), 140.49, 135.98, 133.31 (d, J(CCCF) = 9.9 Hz), 130.83, 128.34
4
2
(d, J(CCCCF) = 2.9 Hz), 123.58, 118.35, 116.54 (d, J(CCF) = 22.4 Hz), 115.62, 114.81, 45.43.
Anal. calcd. For C18H13FN2O3: C, 66.66; H, 4.04; N, 8.64. Found: C, 66,75; H, 3.95; N, 8.52.

ACCEPTED MANUSCRIPT
4.4. The benzylation of N-allylquinazoline-2,4-dione 22 – the general procedure
To a solution of N-allylquinazoline-2,4-dione 22 (1.00 mmol) in acetonitrile (15 mL)
potassium hydroxide (3.00 mmol) was added followed by the respective benzyl chloride (1.10
mmol). The reaction mixture was stirred at 105°C for 4 h. The solvent was removed in vacuo,
the residue was dissolved in methylene chloride (10 mL) and washed with water (3 × 10 mL).
The organic layer was dried (MgSO4), concentrated and the crude product was purified by
column chromatography with methylene chloride-hexane mixture (7:3, v/v) and further
crystallized from a chloroform-petroleum ether mixture.
4.4.1. 1-Allyl-3-benzyl-1H-quinazoline-2,4-dione (19a)
An amorphous solid, m.p. = 85–86°C. IR (KBr, cm–1) νmax: 3085, 2853, 1699, 1657, 1609,
1484, 1456, 1435, 1269, 946, 759. 1H NMR (600 MHz, CDCl3): δ = 8.28–8.27 (m, 1H), 7.68–
7.64 (m, 1H), 7.55–7.74 (m, 2H), 7.34–7.32 (m, 2H), 7.29–7.25 (m, 2H), 7.19–7.18(m, 1H),
3
5.95 (ddt, J = 17.0 Hz, 3J = 10.3 Hz, 3J = 5.0 Hz, 1H, CH2–CH=CH2), 5.32 (s, 2H, CH2Ph),
5.29 (d, 3J = 10.3 Hz, 1H, CH2–CH=CHH), 5.23 (d, 3J = 17.3 Hz, 1H, CH2–CH=CHH), 4.80
(d, 3J = 4.9 Hz, 2H, CH2–CH=CH2); 13C NMR (150 MHz, CDCl3): δ = 161.76 (C=O), 150.85
(C=O), 139.90, 137.05, 134.99, 131.30, 129.16, 128.99, 128.42, 122.97, 117.64, 115.75,
114.14, 46.04, 45.05. Anal. calcd. For C18H16N2O2: C, 73.95; H, 5.52; N, 9.58. Found: C,
73.59; H, 5.52; N, 9.61.
4.4.2. 1-Allyl-3-(2-fluoro)benzyl-1H-quinazoline-2,4-dione (19b)
An amorphous solid, m.p. = 105–107°C. IR (KBr, cm–1) νmax: 3090, 3067, 2975, 1707, 1661,
1608, 1480, 1416, 1290, 975, 917, 752. 1H NMR (600 MHz, CDCl3): δ = 8.28 (d, J = 7.9 Hz,
1H), 7.69–7.66 (m, 1H), 7.31–7.26 (m, 2H), 7.26–7.21 (m, 2H), 7.08–7.06 (m, 2H), 5.95 (ddt,
3J = 17.3 Hz, 3J = 10.2 Hz, 3J = 5.0 Hz, 1H, CH2–CH=CH2), 5.42 (s, 2H, CH2Ph), 5.29 (d, 3J
= 10.2 Hz, 1H, CH2–CH=CHH), 5.24 (d, 3J = 17.3 Hz, 1H, CH2–CH=CHH), 4.82 (d, 3J = 5.0
Hz, 2H, CH2–CH=CH2); 13C NMR (150 MHz, CDCl3): δ = 161.68 (C=O), 160.80 (d, 1J(CF)
=
4
247.6 Hz), 150.70 (C=O), 139.95, 135.10, 131.24, 129.24, 129.23 (d, J(CCCCF) = 3.0 Hz),
3
3
2
128.95 (d, J(CCCF) = 7.9 Hz), 124.04 (d, J(CCCF) = 3.9 Hz), 123.92 (d, J(CCF) = 14.3 Hz),

ACCEPTED MANUSCRIPT
2
3
123.05, 117.66, 115.62, 115.48 (d, J(CCF) = 21.8 Hz), 114.21, 46.03, 38.93 (d, J(CCCF) = 4.7
Hz). Anal. calcd. For C18H15FN2O2: C, 69.67; H, 4.87; N, 9.03. Found: C, 69.75; H, 4.53; N,
9.14.
4.4.3. 1-Allyl-3-(3-fluoro)benzyl-1H-quinazoline-2,4-dione (19c)
An amorphous solid, m.p. = 85–86°C. IR (KBr, cm–1) νmax: 3083, 3017, 1701, 1656, 1483,
1401, 1346, 1209, 978, 943, 760. 1H NMR (600 MHz, CDCl3): δ = 8.28–8.27 (m, 1H), 7.68–
7.66 (m, 1H), 7.32–7.27 (m, 3H), 7.24–7.20 (m, 2H), 6.98–6.96 (m, 1H), 5.95 (ddt, 3J = 17.2
3
3
Hz, J = 10.2 Hz, J = 5.0 Hz, 1H, CH2–CH=CH2), 5.30–5.29 (m, 3H, CH2Ph, CH2–
3
3
CH=CHH), 5.24 (d, J = 17.2 Hz, 1H, CH2–CH=CHH), 4.81 (d, J = 5.0 Hz, 2H, CH2–
13
1
CH=CH2); C NMR (150 MHz, CDCl3): δ = 162.83 (d, J(CF) = 245.8 Hz), 161.69 (C=O),
150.77 (C=O), 139.90, 139.40 (d, 3J(CCCF) = 7.6 Hz), 135.14, 131.20, 129.80 (d, 3J(CCCF) = 7.9
4
2
Hz), 129.18, 124.52 (d, J(CCCCF) = 3.1 Hz), 123.09, 117.72, 115.78 (d, J(CCF) = 21.9 Hz),
115.62, 114.53 (d, 2J(CCF) = 21.0 Hz), 114.21, 46.08, 45.05 (d, 4J(CCCCF) = 1.5 Hz). Anal. calcd.
For C18H15FN2O2: C, 69.67; H, 4.87; N, 9.03. Found: C, 69.71; H, 4.48; N, 9.00.
4.4.4. 1-Allyl-3-(4-fluoro)benzyl-1H-quinazoline-2,4-dione (19d)
An amorphous solid, m.p. = 94.0–95.5°C. IR (KBr, cm–1) νmax: 3092, 3021 2964, 1702, 1657,
1603, 1483, 1436, 1216, 1159, 961, 751. 1H NMR (600 MHz, CDCl3): δ = 8.28–8.26 (m, 1H),
7.67–7.64 (m, 1H), 7.57–7.54 (m, 2H), 7.29–7.26 (m, 1H), 7.20–7.18 (m, 1H), 7.02–6.99 (m,
2H), 5.98 (ddt, 3J = 17.1 Hz, 3J = 10.2 Hz, 3J = 5.0 Hz, 1H, CH2–CH=CH2), 5.29 (d, 3J = 10.2
3
Hz, 1H, CH2–CH=CHH), 5.27 (s, 2H, CH2Ph), 5.23 (d, J = 17.1 Hz, 1H, CH2–CH=CHH),
3
1
4.80 (d, J = 5.0 Hz, 2H, CH2–CH=CH2); 13C NMR (150 MHz, CDCl3): δ = 162.31 (d, J(CF)
4
= 246.8 Hz), 161.71 (C=O), 150.78 (C=O), 139.87, 135.07, 132.87 (d, J(CCCCF) = 3.3 Hz),
131.23, 131.05 (d, 3J(CCCF) = 7.6 Hz), 129.12, 123.04, 117.67, 115.67, 115.20 (d, 2J(CCF) = 20.8
Hz), 114.18, 46.03, 44.31. Anal. calcd. For C18H15FN2O2: C, 69.67; H, 4.87; N, 9.03. Found:
C, 69.31; H, 4.59; N, 9.18.
4.5. Cycloadditions of C-(diethoxyphosphoryl)nitrones 16 (R=Me) and 17 (R=Bn) and N1-
allylated quinazoline-2,4-diones 18 and 19 – the general procedure

ACCEPTED MANUSCRIPT
Solutions of nitrones 16 or 17 (1.00 mmol) and the respective N1-allylated quinazoline-2,4-
diones 18 or 19 (1.05 mmol) in toluene or a toluene-ethanol mixture were stirred at 60°C until
the starting nitrone disappeared. Solvents were removed in vacuo and the crude products (the
respective mixtures of isoxazolidines cis-12/trans-12, cis-13/trans-13, cis-14/trans-14 or cis-
15/trans-15) were purified on silica gel columns.
4.5.1. Diethyl trans-{5-[(3-(2-fluorobenzoyl)-2,4-dioxo-3,4-dihydroquinazolin-1(2H)-
yl)methyl]-2-methylisoxazolidin-3-yl}phosphonate (trans-12b)
A colorless oil. IR (film, cm–1) νmax: 3451, 2981, 2924, 1748, 1702, 1666, 1609, 1481, 1390,
1
1234, 1052, 1023, 970, 758. H NMR (600 MHz, CDCl3): δ = 8.24 (d, J = 7.7 Hz, 1H), 8.14
(t, J = 7.5 Hz, 1H), 7.74 (t, J = 7.5 Hz, 1H), 7.76–7.73 (m, 1H), 7.66–7.63 (m, 1H), 7.48 (d, J
= 8.5 Hz, 1H), 7.35–7.31 (m, 2H), 7.12 (dd, J = 11.4 Hz, J = 8.5 Hz, 1H), 4.51 (dd, 2J = 15.1
3
Hz, J = 4.5 Hz, 1H, HCHN), 4.45–4.41 (m, 1H, HC5), 4.23–4.15 (m, 5H, 2 × CH2OP,
HCHN), 3.02–3.00 (m, 1H, HC3), 2.86 (s, 3H, CH3N), 2.66 (dddd, 3J(H4α–P) = 19.6 Hz, 2J(H4α–
3
3
2
= 13.4 Hz, J(H4α–H3) = 7.1 Hz, J(H4β–H5) = 7.1 Hz, 1H, HαC4), 2.45 (dddd, J(H4β–H4α)
=
H4β)
3
3
3
3
13.4 Hz, J(H4β–P) = 13.4 Hz, J(H4β–H5) = 9.6 Hz, J(H4β–H3) = 8.1 Hz, 1H, HβC4), 1.34 (t, J =
7.1 Hz, 3H, 2 × CH3CH2OP); 13 C NMR (151 MHz, CDCl3): δ = 164.62 (C=O), 162.07 (d,
3
1J(CF)=259.7Hz), 160.65 (C=O), 149.65 (C=O), 140.71, 136.81 (d, J(CCCF) = 9.9 Hz), 135.68,
133.06, 128.89, 125.04 (d, 4J(CCCCF) = 3.4 Hz), 123.65, 120.52 (d, 2J(CCF) = 7.8 Hz), 117.16 (d,
3
1
2J(CCF) = 23.2 Hz), 115.76, 115.24, 75.22 (d, J(CCCP) = 7.2 Hz, C5), 63.92 (d, J(CP) = 168.1
Hz, C3), 63.14 (d, 2J(COP) = 6.5 Hz, CH2OP), 62.44 (d, 2J(COP) = 7.2 Hz, CH2OP), 46.27, 45.21,
2
3
3
36.85 (d, J(CCP) = 1.3 Hz, C4), 16.49 (d, J(CCOP) = 5.6 Hz, CH3CH2OP), 16.43 (d, J(CCOP)
=
5.6 Hz, CH3CH2OP); 31P NMR (243 MHz, CDCl3): δ = 21.67. Anal. calcd. for
C24H27FN3O7P: C, 55.49; H, 5.24; N, 8.09. Found: C, 55.77; H, 5.04; N, 8.01.
4.5.2. Diethyl cis-{5-[(3-(3-fluorobenzoyl)-2,4-dioxo-3,4-dihydroquinazolin-1(2H)-
yl)methyl]-2-methylisoxazolidin-3-yl}phosphonate (cis-12c)
A colorless oil. IR (film, cm–1) νmax: 3430, 2983, 1751, 1700, 1666, 1605, 1480, 1447, 1395,
1250, 1050, 1025, 970, 790, 757. (1H NMR signals of cis-12c were extracted from the
1
spectrum of a 94:6 mixture of cis-12c and trans-12c) H NMR (600 MHz, CDCl3): δ = 8.21
(dd, J = 7.9 Hz, J = 1.3 Hz, 1H), 7.88–7.85 (m, 1H), 7.82–7.73 (m, 1H), 7.70–7.65 (m, 1H),

ACCEPTED MANUSCRIPT
7.55–7.50 (m, 2H), 7.40–7.30 (m, 2H), 4.65–4.58 (m, 1H, HC5), 4.35 (dd, J = 14.8 Hz, J =
9.8 Hz, 1H, HCHN), 4.25–4.15 (m, 5H, 2 × CH2OP, HCHN), 2.99–2.94 (very broad m, 1H,
HC3), 2.85 (s, 3H, CH3N), 2.85–2.77 (m, HαC4), 2.48–2.40 (broad m, 1H, HβC4), 1.41 (t, 3J
3
= 7.1 Hz, 3H, CH3CH2OP), 1.40 (t, J = 7.1 Hz, 3H, CH3CH2OP); (13C NMR signals of cis-
12c were extracted from the spectrum of a 40:60 mixture of cis-12c and trans-12c) 13C NMR
13
(151 MHz, CDCl3): δ = C NMR (150 MHz, CDCl3): δ = 167.83 (d, 4J(C(O)CCCF) = 3.0 Hz,
C=O), 162.94 (d, 1J(CF) = 248.5 Hz), 161.23 (C=O), 149.59 (C=O), 141.75, 135.73, 133.89 (d,
3
4
3J(CCCF) = 9.6 Hz), 130.85 (d, J(CCCF) = 4.0 Hz), 128.46, 126.17 (d, J(CCCCF) = 2.1 Hz),
2
123.58, 122.08 (d, J(CCF) = 21.7 Hz), 117.11 (d, 2J(CCF) = 21.7 Hz), 116.24, 115.27, 75.04 (d,
1
2
3J(CCCP) = 6.9 Hz, C5), 63.62 (d, J(CP) = 168.0 Hz, C3), 62.88 (d, J(COP) = 6.7 Hz, CH2OP),
2
3
62.65 (d, J(COP) = 7.2 Hz, CH2OP), 46.59, 45.17, 35.53 (C4), 16.60 (d, J(CCOP) = 5.5 Hz,
3
CH3CH2OP), 16.52 (d, J(CCOP) = 5.6 Hz, CH3CH2OP); 31P NMR (243 MHz, CDCl3): δ =
21.44. Anal. calcd. for C24H27FN3O7P: C, 55.49; H, 5.24; N, 8.09. Found: C, 55.28; H, 5.27;
N, 7.93.
4.5.3. Diethyl trans-{5-[(3-(3-fluorobenzoyl)-2,4-dioxo-3,4-dihydroquinazolin-1(2H)-
yl)methyl]-2-methylisoxazolidin-3-yl}phosphonate (trans-12c)
A colorless oil. IR (film, cm–1) νmax: 3424, 2980, 1752, 1703, 1665, 1608, 1481, 1442, 1389,
1
1262, 1052, 1024, 968, 794. H NMR (600 MHz, CDCl3): δ = 8.24 (dd, J = 7.9 Hz, J = 1.2
Hz, 1H), 7.80–7.75 (m, 2H), 7.70–7.65 (m, 1H), 7.55–7.50 (m, 2H), 7.40–7.32 (m, 2H), 4.54–
4.44 (m, 2H, HCHN, HC5), 4.30–4.15 (m, 5H, 2 × CH2OP, HCHN), 3.10–3.00 (very broad
m, 1H, HC3), 2.89 (s, 3H, CH3N), 2.72 (dddd, 3J(H4α–P) = 17.0 Hz, 2J(H4α–H4β) = 13.4 Hz, 3J(H4α–
H3) = 7.4 Hz, 3J(H4β–H5) = 7.4 Hz, 1H, HαC4), 2.48–2.40 (broad m, 1H, HβC4), 1.35 (t, 3J = 7.1
Hz, 3H, CH3CH2OP), 1.34 (t, 3J = 7.1 Hz, 3H, CH3CH2OP); 13C NMR (151 MHz, CDCl3): δ
= 13C NMR (150 MHz, CDCl3): δ = 167.58 (d, 4J(C(O)CCCF) = 3.0 Hz, C=O), 162.94 (d, 1J(CF)
=
3
249.1 Hz), 160.91 (C=O), 149.67 (C=O), 140.69, 135.93, 133.89 (d, J(CCCF) = 9.6 Hz),
130.89 (d, 3J(CCCF) = 7.7 Hz), 129.02, 126.19 (d, 4J(CCCCF) = 2.4 Hz), 123.86, 122.17 (d, 2J(CCF)
= 21.7 Hz), 117.11 (d, 2J(CCF) = 23.2 Hz), 115.56, 115.26, 75.24 (broad s, C5), 63.62 (d, 1J(CP)
2
2
= 168.0 Hz, C3), 63.27 (d, J(COP) = 6.6 Hz, CH2OP), 62.59 (d, J(COP) = 6.9 Hz, CH2OP),
45.98, 45.57, 35.93 (C4), 16.50 (d, 3J(CCOP) = 5.8 Hz, CH3CH2OP), 16.44 (d, 3J(CCOP) = 5.6 Hz,
CH3CH2OP); 31P NMR (243 MHz, CDCl3): δ = 22.33. Anal. calcd. for C24H27FN3O7P: C,
55.49; H, 5.24; N, 8.09. Found: C, 55.31; H, 5.41; N, 7.94.

ACCEPTED MANUSCRIPT
4.5.4. Diethyl cis-{5-[(3-(4-fluorobenzoyl)-2,4-dioxo-3,4-dihydroquinazolin-1(2H)-
yl)methyl]-2-methylisoxazolidin-3-yl}phosphonate (cis-12d)
A colorless oil. IR (film, cm–1) νmax: 3460, 2923, 1750, 1700, 1699, 1663, 1600, 1485, 1297,
1
1245, 1025, 970, 760. H NMR (600 MHz, CDCl3): δ = 8.22–8.21 (m, 1H), 8.04–8.02 (m,
2H), 7.88–7.86 (m, 1H), 7.76–7.73 (m, 1H), 7.33–7.31 (m, 1H) 7.21–7.18 (m, 2H), 4.63–4.59
2
3
(m, 1H, HC5), 4.35 (dd, J = 14.8 Hz, J = 9.8 Hz, 1H, HCHN), 4.30–4.22 (m, 4H, 2 ×
CH2OP), 4.20 (dd, 2J = 14.8 Hz, 3J = 2.5 Hz, 1H, HCHN), 2.95 (ddd, 3J(H3–H4α) = 9.9 Hz, 3J(H3–
H4β) = 7.7 Hz, 2J(H3–P) = 2.3 Hz, 1H, HC3), 2.85 (s, 3H, CH3N), 2.84 (dddd, 3J(H4α–P) = 18.2 Hz,
2J(H4α–H4β) = 12.7 Hz, 3J(H4α–H3) = 9.9 Hz, 3J(H4β–H5) = 8.8 Hz, 1H, HαC4), 2.39 (dddd, 2J(H4β–H4α)
= 12.7 Hz, 3J(H4β–P) = 11.5 Hz, 3J(H4β–H3) = 7.7 Hz, 3J(H4β–H5) = 3.6 Hz, 1H, HβC4), 1.42 (t, 3J =
13
7.2 Hz, 6H, 2 × CH3CH2OP); C NMR (151 MHz, CDCl3): δ = 167.52 (C=O), 166.92 (d,
3
1J(CF) = 258.5 Hz), 161.25 (C=O), 149.63 (C=O), 141.78, 135.67, 133.34 (d, J(CCCF) = 9.9
4
2
Hz), 128.45, 128.38 (d, J(CCCCF) = 2.4 Hz), 123.52, 116.51 (d, J(CCF) = 22.4 Hz), 116.21,
3
1
115.32, 75.00 (d, J(CCCP) = 7.0 Hz, C5), 63.13 (d, J(CP) = 169.3 Hz, C3), 62.83 (d, 2J(COP)
=
6.7 Hz, CH2OP), 62.63 (d, 2J(COP) = 7.0 Hz, CH2OP), 46.58, 45.22 (d, 3J = 4.2 Hz, 35.55 (C4),
3
3
31
16.59 (d, J(CCOP) = 5.6 Hz, CH3CH2OP), 16.52 (d, J(CCOP) = 5.9 Hz, CH3CH2OP); P NMR
(243 MHz, CDCl3): δ = 22.46. Anal. calcd. for C24H27FN3O7P × H2O: C, 53.63; H, 5.44; N,
7.82. Found: C, 53.68; H, 5.29; N, 7.98.
4.5.5. Diethyl trans-{5-[(3-(4-fluorobenzoyl)-2,4-dioxo-3,4-dihydroquinazolin-1(2H)-
yl)methyl]-2-methylisoxazolidin-3-yl}phosphonate (trans-12d)
A colorless oil. IR (film, cm–1) νmax: 3451, 2963, 1748, 1702, 1664, 1601, 1480, 1390, 1242,
1
1157, 1100, 1020, 971, 757. H NMR (600 MHz, CDCl3): δ = 8.26–8.24 (m, 1H), 8.04–8.02
(m, 2H), 7.78–7.75 (m, 1H), 7.51–7.50 (m, 1H), 7.36–7.34 (m, 1H), 7.21–7.18 (m, 2H), 4.35
2
(dd, J = 15.0 Hz, 3J = 9.8 Hz, 1H, HCHN), 4.46–4.42 (m, 1H, HC5), 4.23–4.16 (m, 5H, 2 ×
3
CH2OP, HCHN), 3.05–2.99 (m, 1H, HC3), 2.88 (s, 3H, CH3N), 2.72 (dddd, J(H4α–P) = 19.4
2
3
3
Hz, J(H4α–H4β) = 12.5 Hz, J(H4α–H3) = 7.0 Hz, J(H4β–H5) = 7.0 Hz, 1H, HαC4), 2.42 (dddd,
2J(H4β–H4α) = 12.5 Hz, 3J(H4β–P) = 12.5 Hz, 3J(H4β–H5) = 10.1 Hz, 3J(H4β–H3) = 8.2 Hz, 1H, HβC4),
3
3
13
1.35 (t, J = 7.1 Hz, 3H, CH3CH2OP), 1.34 (t, J = 7.2 Hz, 3H, CH3CH2OP); C NMR (151
1
MHz, CDCl3): δ = 167.28 (C=O), 166.95 (d, J(CF)=258.5Hz), 160.93 (C=O), 149.69 (C=O),

ACCEPTED MANUSCRIPT
3
4
140.71, 135.81, 133.35 (d, J(CCCF) = 9.9 Hz), 128.98, 128.25 (d, J(CCCCF) = 2.7 Hz), 123.77,
116.53 (d, 2J(CCF) = 22.7 Hz), 115.60, 115.20, 75.15 (d, 3J(CCCP) = 6.7 Hz, C5), 63.91 (d, 1J(CP)
2
2
= 167.9 Hz, C3), 63.14 (d, J(COP) = 6.6 Hz, CH2OP), 62.50 (d, J(COP) = 6.7 Hz, CH2OP),
46.25, 45.54, 36.04 (C4), 16.50 (d, 3J(CCOP) = 5.8 Hz, CH3CH2OP), 16.43 (d, 3J(CCOP) = 5.6 Hz,
CH3CH2OP); 31P NMR (243 MHz, CDCl3): δ = 21.59. Anal. calcd. for C24H27FN3O7P × H2O:
C, 53.63; H, 5.44; N, 7.82. Found: C, 53.80; H, 5.32; N, 8.04.
4.5.6. Diethyl cis-{5-[(3-benzoyl-2,4-dioxo-3,4-dihydroquinazolin-1(2H)-yl)methyl]-2-
benzylisoxazolidin-3-yl}phosphonate (cis-13a)
A colorless oil. IR (film, cm–1) νmax: 3455, 2960, 1749, 1660, 1642, 1490, 1378, 1296, 1089,
1
1180, 1050, 1020, 970, 690. H NMR (600 MHz, CDCl3): δ = 8.13–8.11 (m, 1H), 7.98–7.97
(m, 2H), 7.67–7.65 (m, 1H), 7.52–7.49 (m, 2H), 7.41–7.39 (m, 1H), 7.35–7.34 (m, 2H), 7.30–
2
7.29 (m, 3H), 7.15–7.12 (m, 2H), 4.64–4.62 (m, 1H, HC5), 4.44 (d, J = 13.7 Hz, 1H,
3
HCHPh), 4.31–4.24 (m, 5H, 2 × CH2OP, HCHN), 4.21 (dd, 2J = 14.9 Hz, J = 2.3 Hz, 1H,
2
3
3
HCHN), 3.92 (d, J = 13.7 Hz, 1H, HCHPh), 3.24 (ddd, J(H3–H4α) = 10.2 Hz, J(H3–H4β) = 7.3
2
3
2
3
Hz, J(H3–P) = 3.1 Hz, 1H, HC3), 2.81 (dddd, J(H4α–P) = 18.7 Hz, J(H4α–H4β) = 12.9 Hz, J(H4α–
3
2
3
= 10.2 Hz, J(H4β–H5) = 10.2 Hz, 1H, HαC4), 2.31 (dddd, J(H4β–H4α) = 12.9 Hz, J(H4β–P)
=
H3)
3
3
3
12.9 Hz, J(H4β–H3) = 7.3 Hz, J(H4β–H5) = 4.1 Hz, 1H, HβC4), 1.41 (t, J = 7.1 Hz, 6H, 2 ×
CH3CH2OP); 13C NMR (151 MHz, CDCl3): δ = 168.78 (C=O), 161.25 (C=O), 149.75 (C=O),
141.15, 136.61, 135.65, 134.91, 131.89, 130.47, 129.93, 129.13, 128.31, 128.18, 127.59,
3
123.15, 116.01, 115.08, 75.69 (d, J(CCCP) = 6.6 Hz, C5), 62.94 (d, 2J(COP) = 6.6 Hz, CH2OP),
62.69 (d, 2J(COP) = 7.1 Hz, CH2OP), 62.36 (d,3J(CNCP) = 5.1 Hz,CH2Ph), 60.63 (d, 1J(CP) = 170.1
3
Hz, C3), 47.14 (CH2N), 35.07 (s, C4), 16.61 (d, J(CCOP) = 5.6 Hz, CH3CH2OP), 16.55 (d,
3J(CCOP) = 5.6 Hz, CH3CH2OP); 31P NMR (243 MHz, CDCl3): δ = 22.64. Anal. calcd. for
C30H32N3O7P: C, 62.39; H, 5.58; N, 7.28. Found: C, 62.58; H, 5.53; N, 7.18.
4.5.7. Diethyl trans-{5-[(3-benzoyl-2,4-dioxo-3,4-dihydroquinazolin-1(2H)-yl)methyl]-2-
benzylisoxazolidin-3-yl}phosphonate (trans-13a)
A colorless oil. IR (film, cm–1) νmax: 3455, 3062, 2982, 1750, 1701, 1665, 1608, 1480, 1390,
1
1238, 1052, 1023, 968, 757. H NMR (600 MHz, CDCl3): δ = 8.25–8.23 (m, 1H), 7.98–7.96
(m, 2H), 7.73–7.70 (m, 1H), 7.68–7.66 (m, 1H), 7.52–7.46 (m, 3H), 7.36–7.33 (m, 1H), 7.31–

ACCEPTED MANUSCRIPT
2
3
7.28 (m, 5H), 4.47 (d, J = 14.8 Hz, J = 4.2 Hz, 1H, HCHN), 4.46–4.41 (m, 2H, HC5,
2
HCHN), 4.26–4.17 (m, 5H, 2 × CH2OP, HCHPh), 3.91 (d, J = 13.9 Hz, 1H, HCHPh), 3.30
(ddd, 3J(H3–H4β) = 10.0 Hz, 3J(H3–H4α) = 6.5 Hz, 2J(H3–P) = 2.7 Hz, 1H, HC3), 2.68 (dddd, 3J(H4α–P)
2
3
3
= 19.0 Hz, J(H4α–H4β) = 13.0 Hz, J(H4α–H3) = 6.5 Hz, J(H4β–H5) = 6.5 Hz, 1H, HαC4), 2.38
(dddd, 3J(H4β–P) = 14.9 Hz, 2J(H4β–H4α) = 13.0 Hz, 3J(H4β–H3) = 10.0 Hz, 3J(H4β–H5) = 8.12 Hz, 1H,
3
3
HβC4), 1.35 (t, J = 7.0 Hz, 3H, CH3CH2OP), 1.34 (t, J = 7.0 Hz, 3H, CH3CH2OP); 13C
NMR (151 MHz, CDCl3): δ = 168.52 (C=O), 160.99 (C=O), 149.80 (C=O), 140.81, 136.46,
135.66, 135.04, 131.68, 130.49, 129.64, 129.19, 128.87, 128.16, 127.52, 123.69, 115.59,
115.52, 75.48 (d, 3J(CCCP) = 6.4 Hz, C5), 63.31 (d, 2J(COP) = 6.5 Hz, CH2OP), 62.71 (d,3J(CNCP)
= 3.8 Hz, CH2Ph), 62.51 (d, 2J(COP) = 6.8 Hz, CH2OP), 60.72 (d, 1J(CP) = 170.2 Hz, C3), 45.22
2
3
(CH2N), 35.19 (d, J(CCP) = 1.8 Hz, C4), 16.57 (d, J(CCOP) = 5.7 Hz, CH3CH2OP), 16.49 (d,
3J(CCOP) = 5.6 Hz, CH3CH2OP); 31P NMR (243 MHz, CDCl3): δ = 21.67. Anal. calcd. for
C30H32N3O7P: C, 62.39; H, 5.58; N, 7.28. Found: C, 62.18; H, 5.49; N, 7.07.
4.5.8. Diethyl cis-{2-benzyl-5-[(3-(2-fluorobenzoyl)-2,4-dioxo-3,4-dihydroquinazolin-1(2H)-
yl)methyl]isoxazolidin-3-yl}phosphonate (cis-13b)
A colorless oil. IR (film, cm–1) νmax: 3472, 2978, 1744, 1700, 1662, 1607, 1478, 1389, 1240,
1012, 970, 756. (1H NMR signals of cis-13b were extracted from the spectrum of a 90:10
mixture of cis-13b and trans-13b) 1H NMR (600 MHz, CDCl3): δ = 8.24–8.20 (m, 1H), 8.16–
8.09 (m, 1H), 7.66–7.62 (m, 1H), 7.38–7.34 (m, 4H), 7.32–7.29 (m, 3H), 7.14–7.10 (m, 3H),
3
3
3
3
4.62 (dddd, J(H5–H4α) = 9.9 Hz, J(H5–CH) = 7.4 Hz, J(H5–H4β) = 4.2 Hz, J(H5–CH) = 4.2 Hz, 1H,
HC5), 4.43 (d, 2J = 13.9 Hz, 1H, HCHPh), 4.31–4.18 (m, 5H, 2 × CH2OP, HCHN), 4.19 (dd,
2J = 14.8 Hz, 3J(HC–H5) = 7.3 Hz, 1H, HCHN), 3.92 (d, 2J = 13.9 Hz, 1H, HCHPh), 3.24 (ddd,
3J(H3–H4α) = 9.9 Hz, 3J(H3–H4β) = 7.6 Hz, 2J(H3–P) = 3.1 Hz, 1H, HC3), 2.81 (dddd, 3J(H4α–P) = 18.7
2
3
3
Hz, J(H4α–H4β) = 12.7 Hz, J(H4α–H3) = 9.9 Hz, J(H4β–H5) = 9.9 Hz, 1H, HαC4), 2.41 (dddd,
3
3
3
2J(H4β–H4α) = 12.7 Hz, J(H4β–P) = 12.7 Hz, J(H4β–H3) = 7.6 Hz, J(H4β–H5) = 4.2 Hz, 1H, HβC4),
3
1.41 (t, J = 7.1 Hz, 3H, 2 × CH3CH2OP); (13C NMR signals of cis-13b were extracted from
the spectrum of a 59:41 mixture of cis-13b and trans-13b) 13C NMR (151 MHz, CDCl3): δ =
1
164.89 (C=O), 162.08 (d, J(CF)=259.7 Hz), 160.94 (C=O), 149.57 (C=O), 141.06, 136.66 (d,
3J(CCCF) = 9.7 Hz), 136.60, 135.59, 132.96, 129.96, 128.79, 128.28, 127.56, 124.93 (d,
4J(CCCCF) = 3.8 Hz), 123.08, 120.55 (d, 2J(CCF) = 8.0 Hz), 117.18 (d, 2J(CCF) = 23.2 Hz), 115.96,
3
115.18, 75.67 (d, J(CCCP) = 7.2 Hz, C5), 62.93 (d, 2J(COP) = 6.6 Hz, CH2OP), 62.65 (d, 2J(COP)

ACCEPTED MANUSCRIPT
= 6.6 Hz, CH2OP), 62.69 (d, 3J(CNCP) = 4.0 Hz, CH2Ph), 60.65 (d, 1J(CP) = 170.1 Hz, C3), 47.07
3
3
(CH2N), 35.12 (C4), 16.61 (d, J(CCOP) = 5.7 Hz, CH3CH2OP), 16.55 (d, J(CCOP) = 5.7 Hz,
CH3CH2OP); 31P NMR (243 MHz, CDCl3): δ = 22.61. Anal. calcd. for C30H31FN3O7P: C,
60.50; H, 5.25; N, 7.06. Found: C, 60.41; H, 5.12; N, 6.82 (obtained on a 59:41 mixture of
cis-13b and trans-13b).
4.5.9. Diethyl trans-{2-benzyl-5-[(3-(2-fluorobenzoyl)-2,4-dioxo-3,4-dihydroquinazolin-
1(2H)-yl)methyl]isoxazolidin-3-yl}phosphonate (trans-13b)
A colorless oil. IR (film, cm–1) νmax: 3063, 2930, 1749, 1702, 1666, 1609, 1480, 1454, 1391,
1159, 1051, 1022, 967, 775. (NMR signals of trans-13b were extracted from the spectra of a
10:90 mixture of cis-13b and trans-13b) 1H NMR (600 MHz, CDCl3): δ = 8.24–8.22 (m, 1H),
8.15–8.10 (m, 1H), 7.70–7.67 (m, 1H), 7.66–7.62 (m, 1H), 7.44–7.43 (m, 1H), 7.36–7.27 (m,
2
7H), 7.13–7.09 (m, 1H), 4.47–4.42 (m, 2H, HCHN, HC5), 4.43 (d, J = 13.8 Hz, 1H,
2
3
HCHPh), 4.26–4.20 (m, 4H, 2 × CH2OP), 4.18 (dd, J = 14.8 Hz, J(HC–H5) = 7.1 Hz, 1H,
2
3
3
HCHN), 3.87 (d, J = 13.8 Hz, 1H, HCHPh), 3.28 (ddd, J(H3–H4β) = 9.5 Hz, J(H3–H4α) = 6.5
2
3
2
3
Hz, J(H3–P) = 2.8 Hz, 1H, HC3), 2.67 (dddd, J(H4α–P) = 19.2 Hz, J(H4α–H4β) = 12.8 Hz, J(H4α–
H3) = 6.5 Hz, 3J(H4β–H5) = 6.5 Hz, 1H, HαC4), 2.37 (dddd, 3J(H4β–P) = 14.8 Hz, 2J(H4β–H4α) = 12.8
Hz, 3J(H4β–H3) = 9.5 Hz, 3J(H4β–H5) = 8.0 Hz, 1H, HβC4), 1.34 (t, 3J = 7.1 Hz, 3H, CH3CH2OP),
3
1.33 (t, J = 7.0 Hz, 3H, CH3CH2OP); 13C NMR (151 MHz, CDCl3): δ = 164.62 (C=O),
1
3
162.05 (d, J(CF)=259.4 Hz), 160.66 (C=O), 149.70 (C=O), 140.77, 136.80 (d, J(CCCF) = 9.8
4
Hz), 136.60, 135.60, 133.06, 129.51, 128.78, 128.14, 127.45, 125.05 (d, J(CCCCF) = 3.6 Hz),
2
2
123.60, 120.51 (d, J(CCF) = 8.1 Hz), 117.16 (d, J(CCF) = 23.1 Hz), 115.70, 115.56, 75.50 (d,
2
3
3J(CCCP) = 6.5 Hz, C5), 63.25 (d, J(COP) = 6.6 Hz, CH2OP), 62.76 (d, J(CNCP) = 4.9 Hz,
2
1
CH2Ph), 62.46 (d, J(COP) = 6.7 Hz, CH2OP), 60.84 (d, J(CP) = 169.9 Hz, C3), 44.91 (CH2N),
2
3
3
34.96 (d, J(CCP) = 1.6 Hz, C4), 16.54 (d, J(CCOP) = 5.6 Hz, CH3CH2OP), 16.47 (d, J(CCOP)
=
5.6 Hz, CH3CH2OP); 31P NMR (243 MHz, CDCl3): δ = 21.72. Anal. calcd. for
C30H31FN3O7P: C, 60.50; H, 5.25; N, 7.06. Found: C, 60.58.; H, 5.23; N, 6.97 (obtained on a
10:90 mixture of cis-13b and trans-13b).
4.5.10. Diethyl cis-{2-benzyl-5-[(3-(3-fluorobenzoyl)-2,4-dioxo-3,4-dihydroquinazolin-1(2H)-
yl)methyl]isoxazolidin-3-yl}phosphonate (cis-13c)

ACCEPTED MANUSCRIPT
A colorless oil. IR (film, cm–1) νmax: 3063, 3031, 2982, 2930, 1751, 1702, 1665, 1608, 1480,
1389, 1284, 1159, 1051, 1022, 965, 793. (1H NMR signals of cis-13c were extracted from the
spectrum of a 87:13 mixture of cis-13c and trans-13c) 1H NMR (600 MHz, CDCl3): δ = 8.13–
8.11 (m, 1H), 7.76–7.73 (m, 1H), 7.68–7.66 (m, 1H), 7.51–7.46 (m, 4H), 7.33–7.29 (m, 4H),
3
3
3
7.17–7.12 (m, 1H), 4.63 (dddd, J(H5–H4α) = 10.1 Hz, J(H5–CH) = 8.5 Hz, J(H5–H4β) = 4.0 Hz,
2
3J(H5–CH) = 2.0 Hz, 1H, HC5), 4.44 (d, J = 13.4 Hz, 1H, HCHPh), 4.32–4.24 (m, 5H, 2 ×
CH2OP, HCHN), 4.20 (dd, 2J = 14.6 Hz, 3J = 2.0 Hz, 1H, HCHN), 3.92 (d, 2J = 13.4 Hz, 1H,
HCHPh), 3.24 (ddd, 3J(H3–H4α) = 10.1 Hz, 3J(H3–H4β) = 7.3 Hz, 2J(H3–P) = 3.2 Hz, 1H, HC3), 2.82
(dddd, 3J(H4α–P) = 18.7 Hz, 2J(H4α–H4β) = 13.0 Hz, 3J(H4α–H3) = 10.1 Hz, 3J(H4β–H5) = 10.1 Hz, 1H,
2
3
3
3
HαC4), 2.42 (dddd, J(H4β–H4α) = 13.0 Hz, J(H4β–P) = 11.5 Hz, J(H4β–H3) = 7.3 Hz, J(H4β–H5)
=
3
4.0 Hz, 1H, HβC4), 1.41 (t, J = 7.0 Hz, 3H, 2 × CH3CH2OP); (13C NMR signals of cis-13c
were extracted from the spectrum of a 59:41 mixture of cis-13c and trans-13c) 13C NMR (151
4
1
MHz, CDCl3): δ = 167.89 (d, J(C(O)CCCF) = 3.0 Hz, C=O), 162.93 (d, J(CF) = 248.8 Hz),
3
161.21 (C=O), 149.64 (C=O), 141.13, 136.58, 135.79, 134.06 (d, J(CCCF) = 7.4 Hz), 130.85
(d, 3J(CCCF) = 7.1 Hz), 129.95, 128.31, 128.15, 127.59, 126.16 (d, 4J(CCCCF) = 2.8 Hz), 123.27,
2
2
3
122.05 (d, J(CCF) = 21.7 Hz), 117.07 (d, J(CCF) = 23.2 Hz), 116.11, 114.95, 75.63 (d, J(CCCP)
2
= 6.5 Hz, C5), 62.93 (d, J(COP) = 6.6 Hz, CH2OP), 62.69 (d, 2J(COP) = 6.3 Hz, CH2OP), 62.36
3
1
(d, J(CNCP) = 5.0 Hz, CH2Ph), 60.61 (d, J(CP) = 170.5 Hz, C3), 47.18 (CH2N), 35.04 (C4),
3
3
31
16.62 (d, J(CCOP) = 5.6 Hz, CH3CH2OP), 16.55 (d, J(CCOP) = 5.2 Hz, CH3CH2OP); P NMR
(243 MHz, CDCl3): δ = 22.61. Anal. calcd. for C30H31FN3O7P × H2O: C, 58.82; H, 5.27; N,
6.86. Found: C, 58.64; H, 5.17; N, 6.82 (obtained on a 87:13 mixture of cis-13c and trans-
13c).
4.5.11. Diethyl trans-{2-benzyl-5-[(3-(3-fluorobenzoyl)-2,4-dioxo-3,4-dihydroquinazolin-
1(2H)-yl)methyl]isoxazolidin-3-yl}phosphonate (trans-13c)
A colorless oil. IR (film, cm–1) νmax: 3064, 2983, 2931, 2907, 1752, 1703, 1665, 1608, 1480,
1390, 1285, 1147, 1052, 1023, 965, 756. 1H NMR (600 MHz, CDCl3): δ = 8.24–8.23 (m, 1H),
7.75–7.71 (m, 1H), 7.68–7.66 (m, 1H), 7.49–7.46 (m, 2H), 7.39–7.34 (m, 2H), 7.30–729 (m,
2
6H), 4.48–4.44 (m, 3H, H2CN, HC5), 4.24–4.17 (m, 5H, 2 × CH2OP, H'CHPh), 3.92 (d, J =
3
2
14.0 Hz, 1H, HCHPh), 3.32–3.29 (m, 1H, HC3), 2.69 (dddd, J(H4α–P) = 18.1 Hz, J(H4α–H4β)
=
3
3
12.5 Hz, J(H4α–H3) = 6.1 Hz, J(H4β–H5) = 6.1 Hz, 1H, HαC4), 2.41–2.34 (m, 1H, HβC4), 1.35
(t, 3J = 6.1 Hz, 6H, 2 × CH3CH2OP); 13C NMR (151 MHz, CDCl3): δ = 167.60 (d, 4J(C(O)CCCF)
= 2.9 Hz, C=O), 162.94 (d, 1J(CF) = 245.1 Hz), 160.92 (C=O), 149.71 (C=O), 140.79, 136.38,

ACCEPTED MANUSCRIPT
3
3
135.79, 139.91 (d, J(CCCF) = 7.3 Hz), 130.89 (d, J(CCCF) = 7.8 Hz), 129.64, 128.90, 128.15,
127.53, 126.16 (d, 4J(CCCCF) = 2.4 Hz), 123.78, 122.13 (d, 2J(CCF) = 21.7 Hz), 117.08 (d, 2J(CCF)
3
2
= 23.4 Hz), 115.59, 115.51, 75.48 (d, J(CCCP) = 6.3 Hz, C5), 63.31 (d, J(COP) = 6.4 Hz,
CH2OP), 62.67 (br s, CH2Ph), 62.52 (d, 2J(COP) = 6.7 Hz, CH2OP), 60.75 (d, 1J(CP) = 170.1 Hz,
C3), 45.30 (CH2N), 35.21 (C4), 16.55 (d, 3J(CCOP) = 5.5 Hz, CH3CH2OP), 16.47 (d, 3J(CCOP)
=
5.5 Hz, CH3CH2OP); 31P NMR (243 MHz, CDCl3): δ = 21.58. Anal. calcd. for C30H31FN3O7P
× H2O: C, 58.82; H, 5.27; N, 6.86. Found: C, 58.74; H, 5.19; N, 6.92.
4.5.12. Diethyl cis-{2-benzyl-5-[(3-(4-fluorobenzoyl)-2,4-dioxo-3,4-dihydroquinazolin-1(2H)-
yl)methyl]isoxazolidin-3-yl}phosphonate (cis-13d)
A colorless oil. IR (film, cm–1) νmax: 3460, 3063, 2990, 1750, 1700, 1669, 1610, 1490, 1391,
1252, 1022, 970, 757, 574. (1H NMR signals of cis-13d were extracted from the spectrum of a
92:8 mixture of cis-13d and trans-13d) 1H NMR (600 MHz, CDCl3): δ = 8.13–8.11 (m, 1H),
8.02–7.98 (m, 2H), 7.42–7.40 (m, 1H), 7.35–7.34 (m, 2H), 7.30–7.29 (m, 3H), 7.20–7.12 (m,
2
4H), 4.65–4.61 (m, 1H, HC5), 4.44 (d, J = 13.6 Hz, 1H, HCHPh), 4.32–4.23 (m, 5H, 2 ×
3
2
CH2OP, HCHN), 4.19 (dd, 2J = 14.9 Hz, J(HC–H5) = 2.5 Hz, 1H, HCHN), 3.92 (d, J = 13.6
3
3
2
Hz, 1H, HCHPh), 3.24 (ddd, J(H3–H4α) = 10.3 Hz, J(H3–H4β) = 7.3 Hz, J(H3–P) = 3.2 Hz, 1H,
3
2
3
3
HC3), 2.82 (dddd, J(H4α–P) = 18.7 Hz, J(H4α–H4β) = 13.0 Hz, J(H4α–H3) = 10.3 Hz, J(H4β–H5)
=
2
3
3
8.6 Hz, 1H, HαC4), 2.39 (dddd, J(H4β–H4α) = 13.0 Hz, J(H4β–P) = 11.5 Hz, J(H4β–H3) = 7.3 Hz,
3J(H4β–H5) = 4.1 Hz, 1H, HβC4), 1.42 (t, 3J = 7.1 Hz, 3H, CH3CH2OP), 1.41 (t, 3J = 7.1 Hz, 3H,
CH3CH2OP); (13C NMR signals of cis-13d were extracted from the spectrum of a 85:15
13
mixture of cis-13d and trans-13d) C NMR (151 MHz, CDCl3): δ = 167.58 (C=O), 166.90
(d, 1J(CF)=258.7Hz), 161.22 (C=O), 149.70 (C=O), 141.14, 136.60, 135.74, 133.33 (d, 3J(CCCF)
4
= 9.9Hz), 129.91, 128.39 (d, J(CCCCF) = 2.5 Hz), 128.32, 128.18, 127. 59, 123.22, 116.50 (d,
2J(CCF) = 22.2 Hz), 116.06, 115.01, 75.64 (d, 3J(CCCP) = 6.5 Hz, C5), 62.92 (d, 2J(COP) = 6.7 Hz,
2
CH2OP), 62.69 (d, J(COP) = 6.7 Hz, CH2OP), 62.38 (d,3J(CNCP) = 5.0 Hz,CH2Ph), 60.63 (d,
2
1J(CP) = 170.2 Hz, C3), 47.15 (CH2N), 35.04 (d, J(CCP) = 1.3 Hz, C4), 16.62 (d, 3J(CCOP) = 5.5
Hz, CH3CH2OP), 16.51 (d, 3J(CCOP) = 6.5 Hz, CH3CH2OP); 31P NMR (243 MHz, CDCl3): δ =
22.64. Anal. calcd. for C30H31FN3O7P × H2O: C, 58.82; H, 5.27; N, 6.86. Found: C, 58.93; H,
5.29; N, 6.81 (obtained on a 85:15 mixture of cis-13d and trans-13d).

ACCEPTED MANUSCRIPT
4.5.13. Diethyl trans-{2-benzyl-5-[(3-(4-fluorobenzoyl)-2,4-dioxo-3,4-dihydroquinazolin-
1(2H)-yl)methyl]isoxazolidin-3-yl}phosphonate (trans-13d)
A colorless oil. IR (film, cm–1) νmax: 3458, 2982, 1749, 1701, 1665, 1600, 1479, 1390, 1242,
1
1022, 969, 756. H NMR (600 MHz, CDCl3): δ = 8.24–8.23 (m, 1H), 8.00–7.98 (m, 2H),
7.74–7.71 (m, 1H), 7.47–7.44 (m, 1H), 7.36–7.34 (m, 1H), 7.30–7.27 (m, 5H), 7.19–7.15 (m,
2H), 4.48–4.41 (m, 2H, HC5, HCHN), 4.45 (d, 2J = 13.9 Hz, 1H, HCHPh), 4.27–4.17 (m, 5H,
2 × CH2OP, HCHN), 3.91 (d, 2J = 13.9 Hz, 1H, HCHPh), 3.30 (ddd, 3J(H3–H4β) = 9.5 Hz, 3J(H3–
2
3
2
= 6.6 Hz, J(H3–P) = 2.8 Hz, 1H, HC3), 2.69 (dddd, J(H4α–P) = 19.1 Hz, J(H4α–H4β) = 13.0
H4α)
Hz, 3J(H4α–H3) = 6.6 Hz, 3J(H4β–H5) = 6.6 Hz, 1H, HαC4), 2.37 (dddd, 3J(H4β–P) = 14.9 Hz, 2J(H4β–
3
3
3
= 13.0 Hz, J(H4β–H3) = 9.5 Hz, J(H4β–H5) = 8.1 Hz, 1H, HβC4), 1.35 (t, J = 7.1 Hz, 3H,
H4α)
CH3CH2OP), 1.34 (t, 3J = 7.1 Hz, 3H, CH3CH2OP); 13C NMR (151 MHz, CDCl3): δ = 167.29
1
(C=O), 166.93 (d, J(CF)=258.1Hz), 160.93 (C=O), 149.73 (C=O), 140.79, 136.48, 135.72,
3
4
133.33 (d, J(CCCF) = 9.9Hz), 129.61, 128.88, 128.23 (d, J(CCCCF) = 2.8 Hz), 128.1, 127.50,
2
3
123.73, 116.54 (d, J(CCF) = 22.2 Hz), 115.55, 115.53, 75.43 (d, J(CCCP) = 6.3 Hz, C5), 63.27
3
2
(d, 2J(COP) = 6.3 Hz, CH2OP), 62.69 (d, J(CNCP) = 4.0 Hz, CH2Ph), 62.50 (d, J(COP) = 6.7 Hz,
1
2
CH2OP), 60.77 (d, J(CP) = 169.8 Hz, C3), 45.30 (CH2N), 35.24 (d, J(CCP) = 1.9 Hz, C4),
3
3
31
16.55 (d, J(CCOP) = 5.6 Hz, CH3CH2OP), 16.47 (d, J(CCOP) = 5.8 Hz, CH3CH2OP); P NMR
(243 MHz, CDCl3): δ = 21.64. Anal. calcd. for C30H31FN3O7P × 1.5 H2O : C, 57.88; H, 5.50;
N, 6.75. Found: C, 58.05; H, 5.73; N, 6.81.
4.5.14. Diethyl cis-{5-[(3-benzyl-2,4-dioxo-3,4-dihydroquinazolin-1(2H)-yl)methyl]-2-
methylisoxazolidin-3-yl}phosphonate (cis-14a)
A colorless oil. IR (film, cm–1) νmax: 3477, 2987, 1750, 1700, 1669, 1610, 1490, 1393, 1256,
1017. (NMR signals of cis-14a were extracted from the spectrum of a 75:25 mixture of cis-
14a and trans-14a) 1H NMR (600 MHz, CDCl3): δ = 8.24–8.22 (m, 1H), 7.76–7.74 (m, 1H),
7.67–7.63 (m, 1H), 7.53–7.52 (m, 2H), 7.33–7.30 (m, 2H), 7.26–7.23 (m, 2H), 5.31 (AB, JAB
3
= 13.9 Hz, 1H, HCHN), 5.26 (AB, JAB = 13.9 Hz, 1H, HCHN), 4.60 (dddd, J(H5–H4α) = 9.6
Hz, 3J(H5–CH) = 7.3 Hz, 3J(H5–H4β) = 3.7 Hz, 3J(H5–CH) = 3.7 Hz, 1H, HC5), 4.29–4.22 (m, 5H, 2
3
3
× CH2OP, HCHN), 4.18 (dd, 2J = 14.9 Hz, J = 3.7 Hz, 1H, HCHN), 2.93 (ddd, J(H3–H4α)
=
3
2
4
10.0 Hz, J(H3–H4β) = 7.8 Hz, J(H3–P) = 2.3 Hz, 1H, HC3), 2.82 (d, J = 0.6 Hz, CH3N), 2.84–
2.79 (m, 1H, HαC4), 2.41 (dddd, 2J(H4β–H4α) = 12.8 Hz, 3J(H4β–P) = 12.8 Hz, 3J(H4β–H3) = 7.8 Hz,
3
13
3J(H4β–H5) = 3.7 Hz, 1H, HβC4), 1.41 (t, J = 7.1 Hz, 6H, 2 × CH3CH2OP); C NMR (151

ACCEPTED MANUSCRIPT
MHz, CDCl3): δ = 161.94 (C=O), 151.24 (C=O), 141.15, 137.04, 134.73, 128.97, 128.56,
3
128.40, 127.54, 128.79, 122.93, 115.55, 115.43, 75.08 (d, J(CCCP) = 7.3 Hz, C5), 63.22 (d,
2
2
1J(CP) = 168.7 Hz, C3), 62.83 (d, J(COP) = 6.7 Hz, CH2OP), 62.64 (d, J(COP) = 6.8 Hz,
3
CH2OP), 47.19 (s, CH2N), 45.22 (d, J(CNCP) = 3.6 Hz, CH3N), 44.92 (CH2Ph), 35.67 (d,
3
3
2J(CCP) = 1.7 Hz, C4), 16.59 (d, J(CCOP) = 5.6 Hz, CH3CH2OP), 16.51 (d, J(CCOP) = 5.5 Hz,
CH3CH2OP); 31P NMR (243 MHz, CDCl3): δ = 22.51. Anal. calcd. for C24H30N3O6P: C,
53.19; H, 6.20; N, 8.62. Found: C, 53.35; H, 5.99; N, 8.36 (obtained on a 75:25 mixture of
cis-14a and trans-14a).
4.5.15. Diethyl trans-{5-[(3-benzyl-2,4-dioxo-3,4-dihydroquinazolin-1(2H)-yl)methyl]-2-
methylisoxazolidin-3-yl}phosphonate (trans-14a)
A colorless oil. IR (film, cm–1) νmax: 3474, 2980, 1703, 1660, 1662, 1609, 1483, 1349, 1238,
1
1023, 966, 759. H NMR (600 MHz, CDCl3): δ = 8.26–8.24 (m, 1H), 7.66–7.63 (m, 1H),
7.52–7.51 (m, 2H), 7.40–7.38 (m, 1H), 7.32–7.28 (m, 2H), 7.28–7.24 (m, 2H), 5.32 (AB, JAB
3
= 13.9 Hz, 1H, HCHN), 5.27 (AB, JAB = 13.9 Hz, 1H, HCHN), 4.51 (dd, 2J= 14.9 Hz, J(HC–
H5) = 4.1 Hz, 1H, HCHN), 4.42–4.37 (m, 1H, HC5), 4.21–4.14 (m, 5H, 2 × CH2OP, HCHN),
3
2
3.04–2.98 (m, 1H, HC3), 2.86 (s, CH3N), 2.68 (dddd, J(H4α–P) = 19.3 Hz, J(H4α–H4β) = 12.6
3
3
2
Hz, J(H4α–H3) = 7.1 Hz, J(H4β–H5) = 7.1 Hz, 1H, HαC4), 2.41 (dddd, J(H4β–H4α) = 12.6 Hz,
3
3
3
3J(H4β–P) = 12.6 Hz, J(H4β–H3) = 9.7 Hz, J(H4β–H5) = 4.4 Hz, 1H, HβC4), 1.35 (t, J = 7.3 Hz,
6H, 2 × CH3CH2OP); 13C NMR (151 MHz, CDCl3): δ = 161.63 (C=O), 151.29 (C=O),
140.14, 136.93, 134.87, 128.04, 128.9, 128.40, 127.58, 128.79, 123.16, 115.67, 114.57, 75.35
(d, 3J(CCCP) = 7.3 Hz, C5), 63.95 (d, 1J(CP) = 173.5 Hz, C3), 63.14 (d, 2J(COP) = 6.5 Hz, CH2OP),
62.40 (d, 2J(COP) = 7.1 Hz, CH2OP), 46.24 (CH3N), 45.98 (CH2N), 45.04 (CH2Ph), 35.99 (C4),
3
3
31
16.50 (d, J(CCOP) = 5.9 Hz, CH3CH2OP), 16.45 (d, J(CCOP) = 5.9 Hz, CH3CH2OP); P NMR
(243 MHz, CDCl3): δ = 21.74. Anal. calcd. for C24H30N3O6P × H2O: C, 57.02; H, 6.38; N,
8.31. Found: C, 57.26; H, 6.09; N, 8.33.
4.5.16. Diethyl cis-{5-[(3-(2-fluorobenzyl)-2,4-dioxo-3,4-dihydroquinazolin-1(2H)-
yl)methyl]-2-methylisoxazolidin-3-yl}phosphonate (cis-14b)
A colorless oil. IR (film, cm–1) νmax: 2999, 1780, 1720, 1666, 1617, 1450, 1386, 1249, 1032.
1H NMR (600 MHz, CDCl3): δ = 8.25–8.24 (m, 1H), 7.79–7.77 (m, 1H), 7.68–7.66 (m, 1H),