Arylmethyl substituted derivatives of Fosmidomycin: Synthesis and antimalarial activity

Article abstract of DOI:10.1016/j.ejmech.2006.06.015

The phosphonohydroxamic acid Fosmidomycin is a drug candidate for the treatment of Malaria, currently in phase II trials in combination with Clindamycin. In order to obtain compounds of higher lipophilicity, we recently synthesized α-phenyl substituted Fo

Full text of DOI:10.1016/j.ejmech.2006.06.015

European Journal of Medicinal Chemistry 41 (2006) 1385e1397
http://www.elsevier.com/locate/ejmech
Original article
Arylmethyl substituted derivatives of Fosmidomycin: Synthesis
and antimalarial activity
Katrin Schluter a, Rolf D. Walter b, Barbel Bergmann b, Thomas Kurz a,
*
¨
¨
a Institute of Pharmacy, University of Hamburg, Bundesstraße 45, D-20146 Hamburg, Germany
b Bernhard Nocht Institute for Tropical Medicine, Bernhard-Nocht-Straße 74, D-20359 Hamburg, Germany
Received 19 April 2006; received in revised form 19 June 2006; accepted 22 June 2006
Available online 18 October 2006
Abstract
The phosphonohydroxamic acid Fosmidomycin is a drug candidate for the treatment of Malaria, currently in phase II trials in combination
with Clindamycin. In order to obtain compounds of higher lipophilicity, we recently synthesized a-phenyl substituted Fosmidomycin derivatives
which display high antimalarial activity. We now report the synthesis and in vitro antimalarial activity of arylmethyl substituted bis(pivaloyloxy-
methyl) ester prodrugs of Fosmidomycin and its acetyl analogue FR900098. The 3,4-dichlorobenzyl substituted derivative of Fosmidomycin
proved to be about twice as active as the respective Fosmidomycin prodrug, however, less active than the corresponding FR900098 prodrug.
Electron donating substituents as well as voluminous substituents led to a significant reduction of activity.
Ó 2006 Elsevier Masson SAS. All rights reserved.
Keywords: Fosmidomycin; Chain-substituted analogues; Prodrugs; Plasmodium falciparum; DOXP-pathway
1. Introduction
protozoans, but not in humans. Therefore it represents an
interesting target for the treatment of malaria and bacterial
infectious diseases [3,4]. Clinical trials conducted with Fosmi-
domycin in combination with Clindamycin or Artesunate have
shown high efficiency in the treatment of acute, uncomplicated
Malaria tropica [5]. However, due to its short plasma half time
of approximately 2.5 h and its low oral bioavailability of 30%,
Fosmidomycin needs to be administered repeatedly in
relatively high dosages [6].
Several research groups have contributed to the structural
modification of Fosmidomycin I (Fig. 1) and its more active
acetyl analogue (II) [7e11]. Among these modifications, the
insertion of substituents in the a-position of the propyl chain
seems to be most promising, whereas both the phosphonic
acid and the hydroxamic acid moiety are essential for antima-
larial activity [7,9e11]. Furthermore, various publications re-
late to ester prodrugs of FR900098 with improved in vivo
antimalarial activity in the mouse model [8]. The hygroscop-
icity of Fosmidomycin and its analogues represents a general
disadvantage of phosphonohydroxamic acids. In previous
studies we have found that this drawback can be overcome
Every year up to 3 million people die of Malaria world-
wide. According to estimations by the World Health Organisa-
tion, more than 90% of these deaths occur in sub-Saharan
Africa. Plasmodium falciparum, the causative agent of Malaria
tropica, is responsible for most of the fatal malaria cases. Ex-
cessive use of established drugs such as Chloroquine and Sul-
phadoxine/Pyrimethamine resulted in high rates of resistance
[1]. To overcome these problems, new antimalarial drugs
based on novel modes of action have to be developed. Fosmi-
domycin (I) was found to repress P. falciparum growth by
inhibiting the 1-desoxy-D-xylulose-5-phosphate (DOXP)
reductoisomerase, a key enzyme of the DOXP/MEP pathway
of isoprenoid biosynthesis [2,3]. This pathway is for instance
present in algae, higher plants, several bacteria and
Abbreviations: DOXP, 1-desoxy-D-xylulose-5-phosphate; MEP, 1-C-methyl-D-
erythritol-4-phosphate.
* Corresponding author. Tel.: þ49 40 42838 3467; fax: þ49 40 42838 6573.
E-mail address: kurz@chemie.uni-hamburg.de (T. Kurz).
0223-5234/$ - see front matter Ó 2006 Elsevier Masson SAS. All rights reserved.
doi:10.1016/j.ejmech.2006.06.015

1386
K. Schlu¨ter et al. / European Journal of Medicinal Chemistry 41 (2006) 1385e1397
R
O
O
O
O
P
EtO
i
O
P
EtO
EtO
EtO
R1
O
O
EtO
R1
O
O
P
O
O
P
HO
O
1
2: 59-80%
N
O
HO
N
O
O
OH
OH
ii, iii, iv
O
Fosmidomycin: R = H
Ia: R = H
IIa: R = CH
R
R1
R
O
P
EtO
O
P
v or vi
FR900098: R = CH
3
3
OBn
EtO
N
H
N
OBn
O
Fig. 1. Structures of Fosmidomycin, FR900098 and their bis(pivaloyloxy-
methyl) esters.
EtO
4: R1 = H, 77-97%
3: 48-85%
5: R1 = CH , 87-95%
3
i. RX, n-Buli, toluene
ii: HCl, aceton
iii: BnONH2, MeOH
iv: NaCNBH3, HCl, MeOH
v: HOOCH/Ac2O
vi: AcCl, TEA, CH2Cl2
vii: TMSBr, THF, H2O
viii: ClCH2OOC(CCH3)3
ix: H2, Pd-C
by masking the phosphonic acid moiety as bis(pivaloyloxy-
methyl) esters [11]. We reported the synthesis of a-phenyl
substituted Fosmidomycin analogs and bis(pivaloyloxy-
methyl) ester prodrugs of I and II, which possess biological
activity comparable to FR900098 [9,11]. Recently, these
results were confirmed by Van Calenbergh et al. [10]. In this
paper, we describe the synthesis and antimalarial activity
of arylmethyl substituted bis(pivaloyloxymethyl) esters of
Fosmidomycin and FR900098.
vii, viii
O
R
O
R1
O
O
O
P
N
O
O
OBn
O
ix
O
6: R1 = H, 31-62%
R
R1
O
O
P
7: R1 = CH , 35-82%
2. Chemistry
3
O
N
O
O
O
OH
O
Synthesis of the target compounds (8, 9) started with the
alkylation of dioxolane 1 with the appropriate arylmethyl ha-
lides (AreCH2eX) in the presence of n-BuLi in dry toluene.
Acidic hydrolysis of 2, oximation and subsequent reduction
with sodium cyanoborohydride in acidic medium led to O-pro-
tected hydroxylamines 3 [7a]. Reactions of 3 with aceticefor-
mic anhydride or acetyl chloride furnished hydroxamic acids 4
and 5 in 77e97% and 79e95% yield, respectively. Cleavage
of the phosphonic acid ester functions of 4 and 5 was per-
formed by treatment with bromotrimethyl silane and water
[12]. All phosphonic acids were directly transformed into their
corresponding bis(pivaloyloxymethyl) esters 6 and 7 by
alkylation with chloromethyl pivalate in dry DMF [8,11,13].
In the final step, the O-benzyl group was cleaved by catalytic
hydrogenation to give the final products 8 and 9 (Scheme 1).
Under these reaction conditions, compounds 6e,f and 7e,f
formed the respective tetrahydronaphthyl derivatives (8, 9,e,f).
8: R1 = H, 88-99%
R: substituted arylmethyl
9: R1 = CH , 78-99%
3
Scheme 1. Synthesis of a-substituted bis(pivaloyloxymethyl) ester analogues
of Fosmidomycin and FR900098.
In the course of further investigations, an IC50 value of
0.9 mM was determined for 8c (Table 2). The corresponding
IC50 values obtained for the bis(pivaloyloxymethyl) esters of
the lead structures are 2.1 mM for Ia and 0.4 mM for IIa. Con-
sequently, in this assay 8c is about twice as active as Ia,
however, less active than IIa. The positive influence of the
3,4-dihaloaryl moiety on the biological activity of 8c was
also determined by our group and by Van Calenbergh and
co-workers for phenyl substituted derivatives of Fosmidomy-
cin [10,11]. The inhibition of parasite growth at 1 mM of the
benzyl derivative 8a is comparable to Ia, whereas electron do-
nating substituents lead to a significant reduction of activity
(8b,d, 9b,d). A considerable loss of activity was also observed
for derivatives which contain voluminous substituents such as
tetrahydronaphthyl (8e, 9e,f). In accordance with previous re-
sults, the formyl derivatives are more active than the corre-
sponding acetyl derivatives.
3. Biological activity
The in vitro antimalarial activity of all novel analogues was
evaluated by 8-[3H]hypoxanthine incorporation assay accord-
ing to the method of Desjardins using the chloroquine sensi-
tive strain 3D7 of P. falciparum [14a]. The inhibition of
parasite growth at 100, 10 and 1 mM has been determined
and compared to the bis(pivaloyloxymethyl) esters (Ia, IIa)
of Fosmidomycin (I) and FR900098 (II) (Table 1).
5. Conclusion
The introduction of arylmethyl substituents into the
a-position to the phosphonic acid moiety of Fosmidomycin
and FR900098 as well as masking the phosphonic acid func-
tionality as pivaloyloxymethyl esters led to a series of stable,
non-hygroscopic Fosmidomycin analogues. The most active
compound 8c bears a 3,4-dichlorobenzyl substituent in the
4. Results and discussion
Among the novel Fosmidomycin derivatives, the 3,4-di-
chlorobenzyl substituted analogue 8c was the most active
compound with an inhibition rate of 59% at 1 mM (Table 1).

K. Schlu¨ter et al. / European Journal of Medicinal Chemistry 41 (2006) 1385e1397
1387
Table 1
Inhibition of P. falciparum growth (%) at 100, 10 and 1 mM
Compound
R
100 mM
10 mM
1 mM
Inhibition of P. falciparum growth (%)a
8a
8b
8c
8d
8e
8f
C6H5eCH2e
100
85
58
37
76
38
21
67
14
20
23
24
21
7
38
6
2,5-diCH3eC6H5eCH2e
3,4-diCleC6H5eCH2e
4-MeOeC6H4eCH2e
99
86
59
6
(5,6,7,8)-Tetrahydronaphthalene-2-ylmethyl
(5,6,7,8)-Tetrahydronaphthalene-1-ylmethyl
C6H5eCH2e
2,5-diCH3eC6H5eCH2e
3,4-diCleC6H5eCH2e
4-MeOeC6H4eCH2e
73
99
3
19
10
3
9a
9b
9c
9d
9e
9f
100
72
98
76
12
3
(5,6,7,8)-Tetrahydronaphthalene-2-ylmethyl
(5,6,7,8)-Tetrahydronaphthalene-1-ylmethyl
H
72
99
3
0
Ia
IIa
a
98
100
83
96
32
71
H
Mean values of two independent determinations.
a-position and is approximately twice as active as the
bis(pivaloyloxymethyl) ester of Fosmidomycin (Ia), however,
less active than the corresponding FR900098 prodrug. It
should be noted that all arylmethyl substituted analogues
were tested as racemates. Therefore, the resolution of the race-
mates should lead to improved antimalarial activity. Since the
pivaloyloxymethyl ester prodrugs are converted into the corre-
sponding free phosphonic acids by non-specific esterases, no
animal experiments were necessary so far. Further investiga-
tions regarding the bioavailability of compound 8c are
intended.
chromatography on silica gel with EtOAc and n-hexane
(8:2) as eluents.
6.1.1.1. (1-Benzyl-2-[1,3]dioxolan-2-yl-ethyl)-phosphonic acid
diethyl ester (2a). Yield: 80%. 1H NMR (DMSO-d6),
d (ppm): 1.18, 1.19 (2t, J ¼ 7.10 Hz, 6H, POCH2CH3),
1.52e1.64 (m, 1H, CH2), 1.77e1.88 (m, 1H, CH2), 2.18e
2.29 (m, 1H, PCH ), 2.64e2.73 (m, 1H, CH2), 2.94e3.03
(m, 1H, CH2), 3.66e3.80 (m, 4H, OCH2CH2O), 3.91e4.01
(m, 4H, POCH2CH3), 4.84 (t, J ¼ 5.11 Hz, 1H, OCHO),
7.18e7.31 (m, 5H, aromat.).13C NMR (DMSO-d6), d (ppm):
16.6 (2d, JC,P ¼ 5.6 Hz, POCH2CH3), 32.7 (d, JC,P ¼ 3.1 Hz,
CH2), 34.1 (d, JC,P ¼ 139.4 Hz, PCH), 34.8 (d, JC,P ¼ 3.1 Hz,
CH2), 61.5, 61.6 (2d, JC,P ¼ 6.6 Hz, POCH2CH3), 64.4, 64.5
(OCH2CH2O), 102.3 (d, JC,P ¼ 9.2 Hz, OCHO), 126.6,
128.6, 129.4 (tert., aromat.), 139.6 (CH2C quart., aromat.).
IR: 1238 cmꢀ1 (P]O). Anal. Calcd for C16H25O5P: calculated
C 58.53%, H 7.67%; found C 58.30%, H 7.54%.
6. Experimental
Elemental analyses were carried out with a Heraeus CHNe
OeRapid instrument. IR spectra were recorded on a Shimadzu
1
FT-IR 8300. H NMR (400 MHz) and 13C NMR (100 MHz)
were recorded on a Bruker AMX 400 spectrometer using
tetramethylsilane as internal standard and DMSO-d6 or
CDCl3 as solvent. Melting points were determined on a Mettler
FP 62. High resolution mass spectra were recorded on a VG
70-250S mass spectrometer.
6.1.1.2. [1-(2,5-Dimethyl-benzyl)-2-[1,3]dioxolan-2-yl-ethyl]-
phosphonic acid diethyl ester (2b). Yield: 77%. MP:
46.0 ꢁC. 1H NMR (CDCl3), d (ppm): 1.29 (t, J ¼ 6.95 Hz,
6H, POCH2CH3), 1.64e1.79 (m, 1H, CH2), 1.95e2.15 (m,
1H, CH2), 2.28 (s, 6H, PhCH3), 2.31e2.46 (m, 1H, PCH ),
2.60e2.77 (m, 1H, CH2), 3.07e3.20 (m, 1H, CH2), 3.68e
3.93 (m, 4H, OCH2CH2O), 4.01e4.20 (m, 4H, POCH2CH3),
5.32 (t, J ¼ 5.32 Hz, 1H, OCHO), 6.89e6.95 (m, 2H, aromat.),
6.1. Chemistry
6.1.1. General procedure for the preparation of (1-aryl-
methyl-2-[1,3]dioxolan-2-yl-ethyl)-phosphonic acid diethyl
esters 2aef
Dioxolane 1 (50 mmol) was dissolved in dry toluene
(50 mL), cooled down to ꢀ78 ꢁC and treated with a stoichio-
metric amount of n-butyllithium (2.5 M in toluene). After stir-
ring for 1 h under nitrogen atmosphere, the appropriate
arylmethyl halide (50 mmol) was added in one portion. The
reaction mixture was allowed to warm up to room temperature
and was stirred overnight. A solution of NH4Cl (10%, 50 mL)
was added and the product was extracted with diethyl ether.
The organic layer was dried over Na2SO4, evaporated and
the resulting residue (2aef) was purified by column
Table 2
IC50 values of 8c and pivaloyloxymethyl esters of Fosmidomycin and
FR900098 against P. falciparum
Compound
Activity against P. falciparum
IC50 (mM)a
n
SEMb
8c
Ia
Iia
a
0.9
2.1
0.4
4
6
6
0.1
1.1
0.1
Mean values of four or six independent determinations.
Standard errors of the means.
b

1388
K. Schlu¨ter et al. / European Journal of Medicinal Chemistry 41 (2006) 1385e1397
6.96e7.07 (m, 1H, aromat.). 13C NMR (CDCl3), d (ppm): 16.8
(d, JC,P ¼ 6.1 Hz, POCH2CH3), 19.4, 21.4 (PhCH3), 32.7 (d,
JC,P ¼ 141.3 Hz, PCH), 33.1 (d, JC,P ¼ 3.0 Hz, CH2), 33.2 (d,
JC,P ¼ 3.0 Hz, CH2), 62.1 (2d, JC,P ¼ 4.6 Hz, POCH2CH3),
64.9, 65.0 (OCH2CH2O), 103.1 (d, JC,P ¼ 8.1 Hz, OCHO),
127.6, 130.7, 131.2 (tert., aromat.), 133.7, 135.5 (quart., aro-
mat.), 137.5 (d, JC,P ¼ 13.4 Hz, CH2C quart., aromat.). IR:
1234 cmꢀ1 (P]O). Anal. Calcd for C18H29O5P: calculated
C 60.66%, H 8.20%; found C 60.52%, H 8.40%.
JC,P ¼ 5.5 Hz, POCH2CH3), 65.0 (OCH2CH2O), 103.1 (d,
JC,P ¼ 7.6 Hz, OCHO), 125.8, 126.4, 128.0, 128.2, 128.4
11.3 Hz, CH2C quart., aromat.). IR: 1240 cmꢀ1 (P]O). Anal.
Calcd for C20H27O5P: calculated C 63.48%, H 7.19%; found C
63.09%, H 7.28%.
(tert., aromat.), 132.6, 133.9 (quart., aromat.), 137.2 (d, JC,P
¼
6.1.1.6.
methyl)]-phosphonic acid diethyl ester (2f). Yield: 59%. H
NMR (CDCl3),
(ppm): 1.27 (t, J ¼ 6.93 Hz, 6H,
[2-[1,3]Dioxolan-2-yl-ethyl-1-(naphthalene-1-yl-
1
d
6.1.1.3. [1-(3,4-Dichloro-benzyl)-2-[1,3]dioxolan-2-yl-ethyl]-
phosphonic acid diethyl ester (2c). Yield: 72%. MP:
51.0 ꢁC. 1H NMR (CDCl3), d (ppm): 1.21e1.31 (m, 6H,
POCH2CH3), 1.63e1.78 (m, 1H, CH2), 1.95e2.15 (m, 1H,
CH2), 2.23e2.40 (m, 1H, PCH ), 2.72e2.86 (m, 1H, CH2),
3.02e3.15 (m, 1H, CH2), 3.75e3.96 (m, 4H, OCH2CH2O),
3.98e4.19 (m, 4H, POCH2CH3), 5.01 (t, J ¼ 4.87 Hz, 1H,
OCHO), 7.05e7.15 (m, 1H, aromat.), 7.30e7.42 (m, 2H, aro-
mat.). 13C NMR (CDCl3), d (ppm): 16.8 (2d, JC,P ¼ 5.8 Hz,
POCH2CH3), 32.9 (d, JC,P ¼ 3.5 Hz, CH2), 34.0 (d,
JC,P ¼ 141.3 Hz, PCH), 34.7 (d, JC,P ¼ 3.1 Hz, CH2), 62.2
(2d, JC,P ¼ 5.9 Hz, POCH2CH3), 65.2 (OCH2CH2O), 103.1
(d, JC,P ¼ 9.2 Hz, OCHO), 129.2, 130.5, 131.7 (tert., aromat.),
130.7, 132.5 (quart., aromat.), 140.1 (d, JC,P ¼ 11.5 Hz, CH2C
quart., aromat.). IR: 1240 cmꢀ1 (P]O). Anal. Calcd for
C16H23Cl2O5P: calculated C 48.38%, H 5.84%; found C
48.17%, H 5.98%.
POCH2CH3), 1.73e1.92 (m, 1H, CH2), 2.04e2.18 (m, 1H,
CH2), 2.43e2.65 (m, 1H, PCH ), 3.04e3.27 (m, 1H, CH2),
3.61e3.88 (m, 5H, OCH2CH2O overlapping CH2), 3.98e
4.23 (m, 4H, POCH2CH3), 4.91 (t, J ¼ 5.27 Hz, 1H, OCHO),
7.34e7.60 (m, 4H, aromat.), 7.67e7.87 (m, 2H, aromat.),
8.07e8.13 (m, 1H, aromat.). 13C NMR (CDCl3), d (ppm):
16.8 (d, JC,P ¼ 5.9 Hz, POCH2CH3), 33.2 (d, JC,P ¼ 3.0 Hz,
CH2), 33.3 (d, JC,P ¼ 140.5 Hz, PCH), 33.4 (d, JC,P ¼ 3.2 Hz,
CH2), 62.2 (d, JC,P ¼ 6.5 Hz, POCH2CH3), 64.9, 65.0 (OCH2-
CH2O), 103.1 (d, JC,P ¼ 7.8 Hz, OCHO), 124.2, 125.7, 125.9,
126.5, 127.7, 128.1, 129.2 (tert., aromat.), 132.4, 134.4 (quart.,
aromat.), 135.6 (d, JC,P ¼ 12.9 Hz, CH2C quart., aromat.). IR:
1240 cmꢀ1 (P]O). Anal. Calcd for C20H27O5P: calculated C
63.48%, H 7.19%; found C 63.33%, H 7.28%.
6.1.2. General procedure for the preparation of (1-aryl-
methyl-3-benzyloxyamino-propyl)-phosphonic acid diethyl
esters 3aef
6.1.1.4.
[2-[1,3]Dioxolan-2-yl-ethyl-1-(4-methoxy-benzyl)]-
Dioxolanes 2 (30 mmol) were treated with 2 M HCl
(100 mL) and aceton (10 mL) and heated to 50 ꢁC for 3 h.
Aceton was removed and the aqueous layer was extracted
with dichloromethane (3 ꢂ 30 mL). Afterwards, the organic
layer was dried over MgSO4 and the solvent was evaporated.
Without further purification, the resulting crude aldehydes
were dissolved in MeOH (20 mL), treated with O-benzylhy-
droxylamine (30 mmol) and stirred for 1 h. After addition of
further 430 mL of MeOH, the mixture was treated portionwise
with NaBH3CN (90 mmol). Over a period of 30 min, HCl
(37%, 30 mL) was added dropwise under ice cooling. The
mixture was allowed to warm up to room temperature and an-
other 20 mmol of NaBH3CN were added. After an overall time
of 2 h, the solution was concentrated and treated with aqueous
KOH (10%) under ice cooling until alkaline reaction of the
mixture. The product was extracted three times with CH2Cl2
(50 mL), the organic layers were combined, dried with
MgSO4 and evaporated. The residue was purified by column
chromatography on silica gel (EtOAc/n-hexane 8:2) to give
(1-arylmethyl-3-benzyloxy-amino-propyl)-phosphonic acid
diethyl esters 3 as colourless oils.
phosphonic acid diethyl ester (2d). Yield: 80%. 1H NMR
(CDCl3), d (ppm): 1.28, 1.29 (2t, J ¼ 6.99 Hz, J ¼ 7.14 Hz,
6H, POCH2CH3), 1.64e1.80 (m, 1H, CH2), 1.93e2.06 (m,
1H, CH2), 2.24e2.37 (m, 1H, PCH ), 2.62e2.76 (m, 1H,
CH2), 3.06e3.19 (m, 1H, CH2), 3.68e3.91 (m, 7H, OCH2
CH2O overlapping OCH3), 3.99e4.16 (m, 4H, POCH2CH3),
4.93 (t, J ¼ 5.37 Hz, 1H, OCHO), 6.76e6.89 (m, 2H, aromat.),
7.08e7.21 (m, 2H, aromat.). 13C NMR (CDCl3), d (ppm): 16.8
(2d, JC,P ¼ 5.6 Hz, JC,P ¼ 6.1 Hz, POCH2CH3), 33.0 (d,
JC,P ¼ 3.7 Hz, CH2), 34.4 (d, JC,P ¼ 139.9 Hz, PCH), 34.6
(d, JC,P ¼ 3.2 Hz, CH2), 55.7 (OCH3), 62.1, 62.2 (2d,
JC,P ¼ 6.7 Hz, POCH2CH3), 65.0 (OCH2CH2O), 103.2 (d,
JC,P ¼ 9.0 Hz, OCHO), 114.1 (OCCH tert., aromat.), 130.6
(tert., aromat.), 131.7 (d, JC,P ¼ 12.4 Hz, CH2C quart., aro-
mat.), 158.6 (CH3OC quart., aromat.). IR: 1246 cmꢀ1
(P]O). Anal. Calcd for C17H27O6P: calculated C 56.98%,
H 7.59%; found C 56.58%, H 7.92%.
6.1.1.5.
[2-[1,3]Dioxolan-2-yl-ethyl-1-(naphthalene-2-yl-
1
methyl)]-phosphonic acid diethyl ester (2e). Yield: 68%. H
NMR (CDCl3), d (ppm): 1.18e1.31 (m, 6H, POCH2CH3),
1.70e1.85 (m, 1H, CH2), 1.98e2.12 (m, 1H, CH2), 2.41e
2.56 (m, 1H, PCH ), 2.85e2.98 (m, 1H, CH2), 3.28e3.41
(m, 1H, CH2), 3.66e3.85 (m, 4H, OCH2CH2O), 3.97e4.22
(m, 4H, POCH2CH3), 4.99 (t, J ¼ 5.46 Hz, 1H, OCHO),
7.34e7.68 (m, 4H, aromat.), 7.76e7.84 (m, 3H, aromat.).
13C NMR (CDCl3), d (ppm): 16.8 (POCH2CH3), 33.2 (CH2),
34.2 (d, JC,P ¼ 141.4 Hz, PCH), 35.8 (CH2), 62.2 (2d,
6.1.2.1. [3-Benzyloxyamino-1-benzyl-propyl]-phosphonic acid
diethyl ester (3a). Yield: 85%. 1H NMR (DMSO-d6), d (ppm):
1.19 (t, 6H, J ¼ 7.09 Hz), 1.50e1.78 (m, 2H, CH2), 2.16e2.28
(m, 1H, PCH ), 2.52e2.61 (m, 1H, CH2), 2.73e2.87 (m, 2H,
CH2), 2.95e3.02 (m, 1H, CH2), 3.93e4.03 (m, 4H, POCH2CH3),
4.42 (s, 2H, PhCH2O), 6.55 (t, J ¼ 5.58 Hz, 1H, NH ), 7.09e7.33
(m, 10H, aromat.). 13C NMR (DMSO-d6), d (ppm): 16.2 (2d,

K. Schlu¨ter et al. / European Journal of Medicinal Chemistry 41 (2006) 1385e1397
1389
J ¼ 5.6 Hz, POCH2CH3), 25.4 (d, JC,P ¼ 3.6 Hz, CH2), 34.3 (d,
JC,P ¼ 2.6 Hz, CH2), 34.5 (d, JC,P ¼ 137.8 Hz, PCH), 49.1 (d,
JC,P ¼ 6.6 Hz, NCH2), 60.8, 60.9 (2d, JC,P ¼ 5.9 Hz,
POCH2CH3), 74.9 (PhCH2O), 126.1, 127.2, 127.8, 127.9, 128.1,
128.3, 128.9 (tert., aromat.), 138.3 (quart., aromat.), 139.4 (d,
JC,P ¼ 13.2 Hz, CH2C quart., aromat.). IR: 3249 cmꢀ1 (NeH),
1232 cmꢀ1 (P]O). Anal. Calcd for C21H30NO4P: calculated C
64.44%, H 7.72%, N 3.58%; found C 64.28%, H 7.82%, N 3.66%.
(CH3OC quart., aromat.). IR: 3250 cmꢀ1 (NeH), 1244 cmꢀ1
(P]O). Anal. Calcd for C22H32NO5P: calculated C 62.69%,
H 7.65%, N 3.32%; found C 62.46%, H 7.60%, N 3.17%.
6.1.2.5. [3-Benzyloxyamino-1-(naphthalene-2-yl-methyl)-pro-
pyl]-phosphonic acid diethyl ester (3e). Yield: 48%. 1H
NMR (CDCl3), d (ppm): 1.22e1.35 (m, 6H, POCH2CH3),
1.69e1.97 (m, 2H, CH2), 2.25e2.40 (m, 1H, PCH ), 2.67e
3.13 (m, 3H, CH2), 3.27e3.43 (m, 1H, CH2), 3.98e4.19 (m,
4H, POCH2CH3), 4.47 (dd, JAB ¼ 11.67 Hz, 2H, PhCH2O),
6.97e7.91 (m, 12H, aromat.). 13C NMR (CDCl3), d (ppm):
16.9 (2d, JC,P ¼ 6.1 Hz, JC,P ¼ 6.9 Hz, POCH2CH3), 26.4 (d,
JC,P ¼ 3.2 Hz, CH2), 35.6 (d, JC,P ¼ 2.1 Hz, CH2), 36.0 (d,
JC,P ¼ 140.0 Hz, PCH), 50.4 (d, JC,P ¼ 6.0 Hz, NCH2), 62.1
(2d, JC,P ¼ 7.0 Hz, POCH2CH3), 76.5 (PhCH2O), 125.9,
126.5, 127.7, 127.9, 128.0, 128.1, 128.5, 128.6, 128.7 (tert., ar-
6.1.2.2. [3-Benzyloxyamino-1-(2,5-dimethyl-benzyl)-propyl]-
phosphonic acid diethyl ester (3b). Yield: 56%. 1H NMR
(CDCl3), d (ppm): 1.29e1.32 (m, 6H, POCH2CH3) 1.64e
1.94 (m, 2H, CH2), 2.13e2.32 (m, 7H, PhCH3 overlapping
PCH ), 2.51e2.61 (m, 1H, CH2), 2.88e3.03 (m, 2H, CH2),
3.10e3.19 (m, 1H, CH2), 4.05e4.18 (m, 4H, POCH2CH3),
4.45 (s, 2H, PhCH2O), 5.51 (bs, 1H, NH ), 6.85e7.06 (m,
3H, aromat.), 7.16e7.40 (m, 5H, aromat.). 13C NMR
(CDCl3), d (ppm): 16.7 (POCH2CH3), 19.4, 21.3 (PhCH3),
26.1 (d, JC,P ¼ 2.4 Hz, CH2), 32.9 (d, JC,P ¼ 3.2 Hz, CH2),
34.8 (d, JC,P ¼ 138.0 Hz, PCH), 50.5 (d, JC,P ¼ 5.7 Hz,
NCH2), 62.1 (m, POCH2CH3), 76.5 (PhCH2O), 127.1, 128.2,
128.7, 130.8, 131.3 (tert., aromat.), 133.6, 135.6 (quart., aro-
mat.), 137.6 (d, JC,P ¼ 14.3 Hz, CH2C quart., aromat.), 137.9
(quart., aromat.). IR: 3253 cmꢀ1 (NeH), 1230 cmꢀ1 (P]O).
Anal. Calcd for C23H34NO4P: calculated C 65.85%, H
8.17%, N 3.35%; found C 65.46%, H 8.14%, N 3.42%.
omat.), 132.7, 133.9 (quart., aromat.), 137.3 (d, JC,P
¼
15.3 Hz, CH2C quart., aromat.), 138.2 (quart., aromat.). IR:
3269 cmꢀ1 (NeH), 1232 cmꢀ1 (P]O). Anal. Calcd for
C25H32NO4P: calculated C 68.01%, H 7.31%, N 3.17; found
C 67.75%, H 7.56%, N 2.85%.
6.1.2.6. [3-Benzyloxyamino-1-(naphthalene-1-yl-methyl)-pro-
pyl]-phosphonic acid diethyl ester (3f). Yield: 59%. 1H
NMR (DMSO-d6), d (ppm): 1.19e1.27 (m, 6H, POCH2CH3)
1.53e1.89 (m, 2H, CH2), 2.23e2.43 (m, 1H, PCH ), 2.64e
2.99 (m, 3H, CH2), 3.52e3.66 (m, 1H, CH2), 3.96e4.19 (m,
6H, POCH2CH3 overlapping PhCH2O), 6.49 (t, J ¼ 5.09 Hz,
1H, NH ), 6.96e7.06 (m, 2H, aromat.), 7.18e7.30 (m, 3H, ar-
omat.), 7.38e7.48 (m, 2H, aromat.), 7.50e7.63 (m, 2H, aro-
mat.), 7.78e7.86 (m, 1H, aromat.), 7.91e7.98 (m, 1H,
aromat.), 8.01e8.11 (m, 1H, aromat.). 13C NMR (CDCl3),
d (ppm): 16.9 (m, POCH2CH3), 25.9 (d, JC,P ¼ 4.2 Hz, CH2),
33.2 (d, JC,P ¼ 3.0 Hz, CH2), 35.4 (d, JC,P ¼ 140.1 Hz, PCH),
50.2 (d, JC,P ¼ 5.1 Hz, NCH2), 62.4 (m, POCH2CH3), 76.4
(PhCH2O), 124.1, 125.7, 126.1, 126.6, 127.9, 128.2, 128.7,
128.8, 129.4 (tert., aromat.), 132.2, 134.5 (quart., aromat.),
135.4 (d, JC,P ¼ 15.1 Hz, CH2C quart., aromat.). IR:
3252 cmꢀ1 (NeH), 1234 cmꢀ1 (P]O). Anal. Calcd for
C25H32NO4P: calculated C 68.01%, H 7.31%, N 3.17%; found
C 67.83%, H 7.55%, N 2.75%.
6.1.2.3. [3-Benzyloxyamino-1-(3,4-dichloro-benzyl)-propyl]-
phosphonic acid diethyl ester (3c). Yield: 62%. 1H NMR
(CDCl3), d (ppm): 1.23e1.33 (m, 6H, POCH2CH3), 1.67e
2.02 (m, 2H, CH2), 2.16e2.29 (m, 1H, PCH ), 2.55e2.67
(m, 1H, CH2), 3.01e3.18 (m, 3H, CH2), 4.00e4.16 (m, 4H,
POCH2CH3), 4.74 (s, 2H, PhCH2O), 5.66 (bs, 1H, NH ),
7.01e7.08 (m, 1H, aromat.), 7.25e7.39 (m, 7H, aromat.).
13C NMR (CDCl3), d (ppm): 16.9 (m, POCH2CH3), 26.4 (d,
JC,P ¼ 3.4 Hz, CH2), 34.6 (d, JC,P ¼ 2.7 Hz, CH2), 35.9 (d,
JC,P ¼ 140.0 Hz, PCH), 50.1 (d, JC,P ¼ 6.2 Hz, NCH2), 62.2
(m, POCH2CH3), 76.6 (PhCH2O), 128.2, 128.7, 128.8,
129.0, 130.7, 131.5 (tert., aromat.), 132.6, 138.1, 140.3 (quart.,
aromat.). IR: 3249 cmꢀ1 (NeH), 1232 cmꢀ1 (P]O). Anal.
Calcd for C21H28Cl2NO4P: calculated C 54.79%, H 6.13%,
N 3.04%; found C 54.81%, H 6.30%, N 3.07%.
6.1.3. General procedure for the preparation of [1-aryl-
methyl-3-(benzyloxy-formyl-amino)-propyl]-phosphonic
acid diethyl esters 4aef
6.1.2.4.
[3-Benzyloxyamino-1-(4-methoxy-benzyl)-propyl]-
phosphonic acid diethyl ester (3d). Yield: 48%. 1H NMR
(CDCl3), d (ppm): 1.27e1.34 (m, 6H, POCH2CH3), 1.67e
1.94 (m, 2H, CH2), 2.08e2.24 (m, 1H, PCH ), 2.46e2.60
(m, 1H, CH2), 2.92e3.18 (m, 3H, CH2), 3.76 (s, 3H,
OCH3), 4.03e4.15 (m, 4H, POCH2CH3), 4.59 (s, 2H,
PhCH2O), 6.75e6.87 (m, 2H, aromat.), 7.04e7.14 (m, 2H, ar-
omat.), 7.22e7.39 (m, 5H, aromat.). 13C NMR (CDCl3),
d (ppm): 16.9 (2d, JC,P ¼ 6.1 Hz, POCH2CH3), 26.0 (CH2),
34.5 (d, JC,P ¼ 2.9 Hz, CH2), 36.4 (d, JC,P ¼ 138.6 Hz, PCH),
50.3 (d, JC,P ¼ 6.2 Hz, NCH2), 55.6 (OCH3), 62.1 (2d,
JC,P ¼ 6.8 Hz, POCH2CH3), 76.6 (PhCH2O), 114.3 (OCCH
tert., aromat.), 128.2, 128.7, 128.8, 130.5 (tert., aromat.),
131.7 (d, JC,P ¼ 13.4 Hz, CH2C quart., aromat.), 158.6
Formic acid (500 mmol) was treated with acetic acid anhy-
dride (50 mmol) and the reaction mixture was stirred under ex-
clusion of humidity. After 20 min the solution was cooled to
0 ꢁC, and the respective hydroxylamine 3 (10 mmol), dissolved
in dry THF (20 mL), was added dropwise. After 10 min, the
mixture was allowed to warm up to room temperature and
stirred for another 2 h. The solution was treated with 200 mL
of EtOAc and successively washed with water (3 ꢂ 50 mL),
aqueous KOH (0.1 M, 3 ꢂ 25 mL) and once again with water.
The organic layer was dried over MgSO4 and the solvent was
removed under reduced pressure. The residue was purified
by column chromatography on silica gel with EtOAc to give

1390
K. Schlu¨ter et al. / European Journal of Medicinal Chemistry 41 (2006) 1385e1397
[1-arylmethyl-3-(benzyloxy-formyl-amino)-propyl]-phosphonic
acid diethyl esters 4 as colourless oils.
J ¼ 7.02 Hz, J ¼ 7.04 Hz, 6H, POCH2CH3), 1.72e2.20 (m,
3H, CH2, CH ), 2.37e2.73 (m, 1H, CH2), 3.02e3.22 (m, 1H,
CH2), 3.25e3.85 (m, 5H, CH2 overlapping OCH3), 3.96e
4.26 (m, 4H, POCH2CH3), 4.60e4.94 (m, 2H, PhCH2O),
6.73e7.44 (m, 9H, aromat.), 7.65e8.23 (m, 1H, formyl.).
13C NMR (CDCl3), d (ppm): 16.9 (2d, JC,P ¼ 2.9 Hz,
6.1.3.1. [3-(Benzyloxy-formyl-amino)-1-benzyl-propyl]-phos-
phonic acid diethyl ester (4a). Yield: 91%. 1H NMR
(DMSO-d6), d (ppm): 1.19 (t, J ¼ 7.1 Hz, 6H, POCH2CH3),
1.57e1.87 (m, 2H, CH2), 2.09e2.24 (m, 1H, CH ), 2.57e
2.68 (m, 1H, CH2), 2.94e3.02 (m, 1H, CH2), 3.45e3.78 (m,
2H, CH2), 3.94e4.02 (m, 4H, POCH2CH3), 4.77 (s, 2H,
PhCH2O), 7.19e7.40 (m, 10H, aromat.), 7.76e8.25 (m, 1H,
formyl.). 13C NMR (CDCl3), d (ppm): 16.4, 16.5 (2d,
JC,P ¼ 5.6 Hz, POCH2CH3), 25.4 (CH2), 34.8 (CH2), 35.8 (d,
JC,P ¼ 139.9 Hz, PCH), 42.5 (NCH2), 61.8, 61.9 (2d,
JC,P ¼ 7.1 Hz, JC,P ¼ 7.6 Hz, POCH2CH3), 77.6 (PhCH2O),
126.6, 128.6, 129.1, 129.3 (tert., aromat.), 134.3 (quart., aro-
mat.), 138.9 (d, JC,P ¼ 14.2 Hz, CH2C quart., aromat.), 162.8
(C]O). IR: 1680 cmꢀ1 (C]O), 1233 cmꢀ1 (P]O). Anal.
Calcd for C22H30NO5P: calculated C 63.00%, H 7.21%, N
3.34%; found C 62.55%, H 7.20%, N 3.66%.
POCH2CH3), 25.7 (CH2), 34.2 (CH2), 36.3 (d, JC,P
¼
142.9 Hz, PCH), 42.8 (NCH2), 55.6 (OCH3), 62.2 (m,
POCH2CH3), 76.5 (PhCH2O), 114.4 (OCCH tert., aromat.),
129.1, 129.4, 129.7, 130.4 (tert., aromat.), 131.3, 134.6 (quart.,
aromat.), 158.7 (CH3OC quart., aromat.), 163.2 (C]O). IR:
1682 cmꢀ1 (C]O), 1250 cmꢀ1 (P]O). Anal. Calcd for
C23H32NO6Pmiddot;0.5H2O: calculated C 60.25%, H 7.25%,
N 3.05%; found C 60.02%, H 6.91%, N 2.91%.
6.1.3.5.
[3-(Benzyloxy-formyl-amino)-1-(naphthalene-2-yl-
methyl)-propyl]-phosphonic acid diethyl ester (4e). Yield:
89%. 1H NMR (CDCl3), d (ppm): 1.44e1.60 (m, 6H,
POCH2CH3), 1.97e2.60 (m, 3H, CH2, CH ), 2.84e3.14 (m,
1H, CH2), 3.43e4.06 (m, 3H, CH2), 4.20e4.49 (m, 4H,
POCH2CH3), 4.69e5.12 (m, 2H, PhCH2O), 7.15e8.40 (m,
13H, aromat. overlapping formyl.). 13C NMR (CDCl3),
6.1.3.2. [3-(Benzyloxy-formyl-amino)-1-(2,5-dimethyl-benzyl)-
1
propyl]-phosphonic acid diethyl ester (4b). Yield: 89%. H
NMR (CDCl3), d (ppm): 1.32, 1.33 (2t, J ¼ 7.01 Hz,
J ¼ 7.03 Hz, 6H, POCH2CH3), 1.77e2.17 (m, 3H, CH2, CH ),
2.25, 2.26 (2s, 6H, PhCH3), 2.43e2.69 (m, 1H, CH2), 3.01e
3.81 (m, 3H, CH2), 3.94e4.28 (m, 4H, POCH2CH3),
4.48e4.95 (m, 2H, PhCH2O), 6.75e7.47 (m, 8H, aromat.),
7.61e8.24 (m, 1H, formyl.). 13C NMR (CDCl3), d (ppm):
16.9 (2d, JC,P ¼ 5.5 Hz, JC,P ¼ 5.8 Hz, POCH2CH3), 19.4,
21.3 (PhCH3), 25.8 (d, JC,P ¼ 4.9 Hz, CH2), 32.7 (d,
JC,P ¼ 3.7 Hz, CH2), 34.7 (d, JC,P ¼ 135.4 Hz, PCH), 43.1
(NCH2), 62.3 (m, POCH2CH3), 77.1 (PhCH2O), 127.9, 129.1,
129.4, 129.7, 131.0, 131.2 (tert., aromat.), 133.6, 135.8, 135.9
(quart., aromat.), 137.2 (d, JC,P ¼ 15.7 Hz, CH2C quart., aro-
mat.), 163.2 (C]O). IR: 1676 cmꢀ1 (C]O), 1234 cmꢀ1
(P]O). Anal. Calcd for C24H34NO5P: calculated C 64.42%,
H 7.66%, N 3.13%; found C 64.29%, H 7.68%, N 3.20%.
d (ppm): 16.9 (m, POCH2CH3), 25.8 (CH2), 35.0 (d, JC,P
¼
135.9 Hz, PCH), 35.3 (CH2), 42.8 (NCH2), 62.4 (m,
POCH2CH3), 76.7 (PhCH2O), 126.0, 126.6, 127.6, 127.9,
128.1, 128.7, 129.1, 129.6, 130.4 (tert., aromat.), 132.7,
133.9, 134.5, 137.0 (quart., aromat.), 163.3 (C]O). IR:
1681 cmꢀ1 (C]O), 1236 cmꢀ1 (P]O). Anal. Calcd for
C26H32NO5P: calculated C 66.51%, H 6.87%, N 2.98%; found
C 66.11%, H 6.97%, N 2.85%.
6.1.3.6.
[3-(Benzyloxy-formyl-amino)-1-(naphthalene-1-yl-
methyl)-propyl]-phosphonic acid diethyl ester (4f). Yield:
96%. 1H NMR (CDCl3), d (ppm): 1.18e1.27 (m, 6H,
POCH2CH3), 1.67e1.95 (m, 2H, CH2), 2.12e2.36 (m, 1H,
PCH ), 2.89e3.03 (m, 1H, CH2), 3.36e3.77 (m, 3H, CH2),
3.95e4.12 (m, 4H, POCH2CH3), 4.48e4.72 (m, 2H,
PhCH2O), 7.13e8.16 (m, 13H, aromat. overlapping formyl.).
13C NMR (CDCl3), d (ppm): 16.9, 17.0 (2d, JC,P ¼ 5.5 Hz,
JC,P ¼ 5.8 Hz, POCH2CH3), 26.0 (CH2), 32.9 (CH2), 35.2 (d,
JC,P ¼ 137.1 Hz, PCH), 43.0 (NCH2), 62.4 (m, POCH2CH3),
77.7 (PhCH2O), 124.0, 125.8, 126.2, 126.7, 128.1, 129.0,
129.4, 129.7 (tert., aromat.), 132.1, 134.5 (quart., aromat.),
135.2 (d, JC,P ¼ 15.8 Hz, CH2C quart., aromat.), 163.3
(C]O). IR: 1679 cmꢀ1 (C]O), 1240 cmꢀ1 (P]O). Anal.
Calcd for C26H32NO5P: calculated C 66.51%, H 6.87%, N
2.98%; found C 66.40%, H 7.06%, N 2.86%.
6.1.3.3. [3-(Benzyloxy-formyl-amino)-1-(3,4-dichloro-benzyl)-
1
propyl]-phosphonic acid diethyl ester (4c). Yield: 97%. H
NMR (CDCl3), d (ppm): 1.17, 1.18 (2t, J ¼ 7.09 Hz,
J ¼ 7.11 Hz, 6H, POCH2CH3), 1.47e1.90 (m, 2H, CH2),
2.09e2.34 (m, 1H, PCH ), 2.60e3.00 (m, 2H, CH2), 3.50e
3.83 (m, 2H, CH2), 3.88e4.11 (m, 4H, POCH2CH3), 4.81 (s,
2H, PhCH2O), 7.16e7.63 (m, 8H, aromat.), 7.84e8.33 (m, 1H,
formyl.). 13C NMR (CDCl3), d (ppm): 16.8 (m, POCH2CH3),
25.8 (d, JC,P ¼ 5.6 Hz, CH2), 34.3 (CH2), 35.7 (d, JC,P
¼
141.5 Hz, PCH), 42.6 (NCH2), 62.5 (m, POCH2CH3), 78.1
(PhCH2O), 129.1, 129.2, 129.6, 129.8, 130.8, 131.5 (tert., aro-
mat.), 132.7, 134.5, 139.6 (quart., aromat.), 163.4 (C]O). IR:
1677 cmꢀ1 (C]O), 1232 cmꢀ1 (P]O). Anal. Calcd for C22H28
Cl2NO5P: calculated C 54.11%, H 5.78%, N 2.87%; found C
53.98%, H 5.95%, N 2.79%.
6.1.4. General procedure for the preparation of [3-(acetyl-
benzyloxy-amino)-1-arylmethyl-propyl]-phosphonic
diethyl esters 5aef
acid
A solution of the respective hydroxylamine (3; 10 mmol) in
dry CH2Cl2 (10 mL) was cooled to 0 ꢁC and treated succes-
sively with triethylamine (12 mmol) and with acetyl chloride
(12 mmol). The ice bath was removed, and the mixture was
stirred at room temperature for 2 h. After removal of the sol-
vent under reduced pressure, the residue was dissolved in
6.1.3.4. [3-(Benzyloxy-formyl-amino)-1-(4-methoxy-benzyl)-
propyl]-phosphonic acid diethyl ester (4d). Yield: 77%. MP:
43.4 ꢁC. 1H NMR (CDCl3), d (ppm): 1.30, 1.31 (2t,

K. Schlu¨ter et al. / European Journal of Medicinal Chemistry 41 (2006) 1385e1397
1391
EtOAc (100 mL) and washed with 10% K2CO3 solution
(2 ꢂ 50 mL) and 1 M HCl (2 ꢂ 50 mL). The organic layer
was dried over MgSO4, evaporated, and the residue was
purified by column chromatography on silica gel with EtOAc
as an eluent to give [3-(acetyl-benzyloxy-amino)-1-aryl-
methyl-propyl]-phosphonic acid diethyl esters 5 as colourless
oils.
JC,P ¼ 140.7 Hz, PCH), 43.8 (NCH2), 62.3 (2d, JC,P ¼ 7.2 Hz,
JC,P ¼ 7.1 Hz, POCH2CH3), 76.7 (PhCH2O), 129.0, 129.1,
129.4, 129.6, 130.7, 131.5 (tert., aromat.), 130.9, 132.7,
134.7 (quart., aromat.), 139.9 (d, JC,P ¼ 14.5 Hz, CH2C
quart., aromat.), 172.1 (C]O). IR: 1655 cmꢀ1 (C]O),
1227 cmꢀ1 (P]O). Anal. Calcd for C23H30Cl2NO5P: calcu-
lated C 54.99%, H 6.02%, N 2.79%; found C 55.01%, H
6.24%, N 3.14%.
6.1.4.1. [3-(Acetyl-benzyloxy-amino)-1-benzyl-propyl]-phos-
phonic acid diethyl ester (5a). Yield: 92%. 1H NMR
(DMSO-d6), d (ppm): 1.19 (t, J ¼ 7.1 Hz, 6H, POCH2CH3),
1.56e1.70 (m, 4H, CH2 overlapping acetyl. CH3), 1.72e1.86
(m, 1H, CH2), 2.12e2.24 (m, 1H, PCH ), 2.55e2.68 (m, 1H,
CH2), 2.93e3.01 (m, 1H, CH2), 3.51e3.58 (m, 1H, CH2),
3.71e3.81 (m, 1H, CH2), 3.94e4.02 (m, 4H, POCH2CH3),
4.74 (s, 2H, PhCH2O), 7.18e7.40 (m, 10H, aromat.), 13C
NMR (CDCl3), d (ppm): 16.4, 16.5 (2d, JC,P ¼ 6.1 Hz,
POCH2CH3), 20.5 (acetyl. CH3), 25.4 (d, JC,P ¼ 3.1
6.1.4.4.
propyl]-phosphonic acid diethyl ester (5d). Yield: 87%. H
NMR (CDCl3),
[3-(Acetyl-benzyloxy-amino)-1-(4-methoxy-benzyl)-
1
d
(ppm): 1.20 (t, J ¼ 6.98 Hz, 6H,
POCH2CH3), 1.55e1.84 (m, 2H, CH2), 1.95 (s, 3H, acetyl.
CH3), 2.05e2.22 (m, 1H, PCH ), 2.85e2.97 (m, 1H, CH2),
3.48e3.64 (m, 2H, CH2), 3.70 (s, 3H, OCH3), 3.73e3.84
(m, 1H, CH2), 3.93e4.05 (m, 4H, POCH2CH3), 4.73 (s, 2H,
PhCH2O), 6.80e6.85 (m, 2H, aromat.), 7.13e7.18 (m, 2H, ar-
omat.), 7.29e7.40 (m, 5H, aromat.). 13C NMR (CDCl3),
d (ppm): 16.9 (2d, JC,P ¼ 6.1 Hz, JC,P ¼ 5.8 Hz, POCH2CH3),
Hz, CH2), 34.8 (d, JC,P ¼ 2.5 Hz, CH2), 35.8 (d, JC,P
¼
139.9 Hz, PCH), 43.7 (NCH2), 61.8 (2d, JC,P ¼ 6.6 Hz,
JC,P ¼ 7.1 Hz, POCH2CH3), 76.1 (PhCH2O), 126.5, 128.5,
128.6, 128.9, 129.1, 129.2 (tert., aromat.), 134.4 (quart., aro-
mat.), 139.2 (d, JC,P ¼ 14.3 Hz, CH2C quart., aromat.), 172.0
(C]O). IR: 1662 cmꢀ1 (C]O), 1234 cmꢀ1 (P]O).
HRFAB-MS C23H32NO5P [M þ H]þ: calculated 434.2096;
found 434.2122.
20.9 (acetyl. CH3), 25.6 (JC,P ¼ 3.0 Hz, CH2), 34.2 (d, JC,P ¼
2.6 Hz, CH2), 36.3 (d, JC,P ¼ 139.6 Hz, PCH), 44.2 (NCH2),
55.6 (OCH3), 62.3 (m, POCH2CH3), 76.5 (PhCH2O), 114.3
(OCCH tert., aromat.), 129.1, 129.3, 129.5, 130.5 (tert., aro-
mat.), 131.5 (d, JC,P ¼ 15.0 Hz, CH2C quart., aromat.), 134.8
(quart., aromat.), 158.7 (CH3OC quart., aromat.), 172.4
(C]O). IR: 1664 cmꢀ1 (C]O), 1250 cmꢀ1 (P]O). Anal.
Calcd for C24H34NO6P: calculated C 62.19%, H 7.39%, N
3.02%; found C 62.64%, H 7.45%, N 2.77%.
6.1.4.2. [3-(Acetyl-benzyloxy-amino)-1-(2,5-dimethyl-benzyl)-
1
propyl]-phosphonic acid diethyl ester (5b). Yield: 91%. H
NMR (CDCl3), d (ppm): 1.23e1.37 (m, 6H, POCH2CH3),
1.79e1.93 (m, 2H, CH2), 1.97 (s, 3H, acetyl. CH3), 2.06e
2.18 (m, 1H, PCH ), 2.24 (s, 3H, PhCH3), 2.25 (s, 3H,
PhCH3), 2.50e2.64 (m, 1H, CH2), 3.07e3.21 (m, 1H, CH2),
3.50e3.83 (m, 2H, CH2), 4.01e4.21 (m, 4H, POCH2CH3),
4.65 (s, 2H, PhCH2O), 6.88e7.06 (m, 3H, aromat.), 7.21e
7.41 (m, 5H, aromat.). 13C NMR (CDCl3), d (ppm): 16.5 (2d,
JC,P ¼ 6.1 Hz, POCH2CH3), 19.0, 20.9 (PhCH3), 20.5 (acetyl.
CH3), 25.4 (d, JC,P ¼ 3.4 Hz, CH2), 32.3 (d, JC,P ¼ 2.5 Hz,
CH2), 34.4 (d, JC,P ¼ 139.4 Hz, PCH), 43.8 (NCH2), 62.1 (2d,
JC,P ¼ 6.8 Hz, JC,P ¼ 6.6 Hz, POCH2CH3), 76.0 (PhCH2O),
127.2, 128.6, 128.8, 129.1, 130.5, 130.8 (tert., aromat.),
133.1, 135.3, 137.0 (quart., aromat.), 137.6 (d, JC,P ¼ 14.3 Hz,
CH2C quart., aromat.), 175.5 (C]O). IR: 1664 cmꢀ1 (C]O),
1232 cmꢀ1 (P]O). HRFAB-MS C25H36NO5P [M þ H]þ: cal-
culated 462.2409; found 462.2425.
6.1.4.5.
[3-(Acetyl-benzyloxy-amino)-1-(naphthalene-2-yl-
methyl)-propyl]-phosphonic acid diethyl ester (5e). Yield:
95%. MP: 78.5 ꢁC. H NMR (CDCl3), d (ppm): 1.20e1.36
1
(m, 6H, POCH2CH3), 1.78e2.10 (m, 5H, acetyl. CH3 overlap-
ping CH2), 2.17e1.32 (m, 1H, PCH ), 2.74e2.90 (m, 1H,
CH2), 3.26e3.41 (m, 1H, CH2), 3.53e3.91 (m, 2H, CH2),
4.04e4.19 (m, 4H, POCH2CH3), 4.95 (s, 2H, PhCH2O),
7.09e7.50 (m, 8H, aromat.), 7.63e7.84 (m, 4H, aromat.). 13
C
NMR (CDCl3), d (ppm): 16.9 (2d, JC,P ¼ 5.7 Hz, POCH2CH3),
20.9 (acetyl. CH3), 25.8 (CH2), 35.4 (d, JC,P ¼ 2.7 Hz, CH2),
35.8 (PCH), 44.2 (NCH2), 62.3 (m, POCH2CH3), 76.5
(PhCH2O), 125.9, 126.5, 127.7, 128.0, 128.1, 128.6, 129.0,
129.2, 129.4 (tert., aromat.), 132.7, 133.9, 134.7 (quart., aro-
mat.), 137.0 (d, JC,P ¼ 15.0 Hz, CH2C quart., aromat.), 175.5
(C]O). IR: 1651 cmꢀ1 (C]O), 1227 cmꢀ1 (P]O). Anal.
Calcd for C27H34NO5P: calculated C 67.07%, H 7.09%, N
3.20%; found C 67.16%, H 7.14%, N 2.99%.
6.1.4.3. [3-(Acetyl-benzyloxy-amino)-1-(3,4-dichlor-benzyl)-
propyl]-phosphonic acid diethyl ester (5c). Yield: 95%. MP:
66.8 ꢁC. 1H NMR (CDCl3), d (ppm): 1.24e1.33 (m, 6H,
POCH2CH3), 1.68e1.85 (m, 1H, CH2), 1.90e2.19 (m, 5H,
acetyl. CH3 overlapping PCH, CH2), 2.56e2.72 (m, 1H,
CH2), 2.98e3.10 (m, 1H, CH2), 3.59e3.89 (m, 2H, CH2),
3.97e4.16 (m, 4H, POCH2CH3), 4.74 (s, 2H, PhCH2O),
7.00e7.10 (m, 1H, aromat.), 7.23e7.46 (m, 7H, aromat.).
13C NMR (CDCl3), d (ppm): 16.8 (2d, JC,P ¼ 6.1 Hz,
JC,P ¼ 6.0 Hz, POCH2CH3), 20.9 (acetyl. CH3), 25.8 (d,
JC,P ¼ 2.8 Hz, CH2), 34.4 (d, JC,P ¼ 2.8 Hz, CH2), 35.9 (d,
6.1.4.6.
[3-(Acetyl-benzyloxy-amino)-1-(naphthalene-1-yl-
methyl)-propyl]-phosphonic acid diethyl ester (5f). Yield:
94%. 1H NMR (CDCl3), d (ppm): 1.29e1.37 (m, 6H,
POCH2CH3), 1.81 (s, 3H, acetyl. CH3), 1.84e2.03 (m, 2H,
CH2), 2.20e2.40 (m, 1H, PCH ), 2.83e2.98 (m, 1H, CH2),
3.37e3.84 (m, 3H, CH2), 4.04e4.23 (m, 4H, POCH2CH3),
4.50 (s, 2H, PhCH2O), 7.10e7.20 (m, 2H, aromat.), 7.28e
7.39 (m, 5H, aromat.), 7.44e7.55 (m, 2H, aromat.), 7.68e7.76
(m, 1H, aromat.), 7.81e7.88 (m, 1H, aromat.), 8.01e8.07
(m, 1H, aromat.). 13C NMR (CDCl3), d (ppm): 16.9, 17.0

1392
K. Schlu¨ter et al. / European Journal of Medicinal Chemistry 41 (2006) 1385e1397
(2d, JC,P ¼ 5.6 Hz, JC,P ¼ 6.0 Hz, POCH2CH3), 20.7 (acetyl.
CH3), 26.0 (d, JC,P ¼ 3.0 Hz, CH2), 33.2 (d, JC,P ¼ 2.6 Hz,
CH2), 35.1 (d, JC,P ¼ 139.4 Hz, PCH), 44.2 (NCH2), 62.4 (d,
JC,P ¼ 6.2 Hz, POCH2CH3), 76.3 (PhCH2O), 124.1, 125.8,
126.0, 126.6, 127.9, 128.2, 129.0, 129.2, 129.4, 129.5 (tert.,
C 60.90%, H 7.16%, N 2.37%; found C 60.79%, H 7.07%,
N 2.46%.
6.1.5.2. 2,2-Dimethyl-propionic acid [3-(benzyloxy-formyl-
amino)-1-(2,5-dimethyl-benzyl)-propyl]-(2,2-dimethyl-propio-
nyloxymethoxy)-phosphinoyloxymethyl ester (6b). Yield: 44%.
1H NMR (DMSO-d6), d (ppm): 1.16, 1.17 (2s, 18H, C(CH3)3),
1.62e1.91 (m, 2H, CH2), 2.18 (s, 6H, PhCH3), 2.22e2.35 (m,
1H, CH ), 2.89e3.01 (m, 1H, CH2), 3.22e3.33 (m, 1H, CH2),
3.41e3.68 (m, 2H, CH2), 4.56e4.78 (m, 2H, PhCH2O), 5.55e
5.75 (m, 4H, OCH2O), 6.87e7.11 (m, 3H, aromat.), 7.18e
7.43 (m, 5H, aromat.), 7.73e8.18 (m, 1H, formyl.). 13C
NMR (DMSO-d6), d (ppm): 18.8, 20.8 (2s, PhCH3), 24.8
(CH2), 26.8 (C(CH3)3), 31.4 (d, JC,P ¼ 1.8 Hz, CH2), 34.4 (d,
JC,P ¼ 138.9 Hz, PCH), 38.6 (C(CH3)3), 41.8 (NCH2), 76.9
(PhCH2O), 81.8 (OCH2O), 127.7, 128.7, 129.1, 129.8, 130.7
(tert., aromat.), 133.2, 135.1 (quart., aromat.), 136.4 (d,
JC,P ¼ 15.0 Hz, CH2C quart., aromat.), 162.9 (C]O, hydrox-
amate), 176.6 (C]O, ester). IR: 1755 cmꢀ1 (C]O, ester),
1675 cmꢀ1 (C]O, hydroxamate), 1255 cmꢀ1 (P]O). Anal.
Calcd for C32H46NO9P: calculated C 62.02%, H 7.48%, N
2.26%; found C 61.64%, H 7.57%, N 2.31%.
aromat.), 132.1, 134.5 (quart., aromat.), 135.4 (d, JC,P
¼
15.7 Hz, CH2C quart., aromat.), 172.8 (C]O). IR:
1666 cmꢀ1 (C]O), 1232 cmꢀ1 (P]O). Anal. Calcd for
C27H34NO5P: calculated C 67.07%, H 7.09%, N 3.20%; found
C 66.68%, H 7.30%, N 2.90%.
6.1.5. General procedure for the preparation of [3-(acyl-ben-
zyloxy-amino)-1-arylmethyl-propyl]-(2,2-dimethyl-propio-
nyloxymethoxy)-phosphinoyloxymethyl esters 6aef, 7aef
Trimethylsilylbromide (15 mmol) was added to a stirred so-
lution of the phosphonic acid diethyl esters 4aef, 5aef
(3 mmol) in dry CH2Cl2 (10 mL) at 0 ꢁC. After 1 h, the solu-
tion was allowed to warm up to room temperature and was
stirred overnight. The solvent was removed under reduced
pressure and the residue was dissolved in dry THF (10 mL)
and treated with water (0.1 mL) for 5 min. The solvent was
evaporated and the residue was dried at the vacuum pump in
order to remove remaining traces of water. For the alkylation
step, the resulting oil was dissolved in anhydrous DMF
(20 mL), treated with triethylamine (9 mmol) and stirred
for 5 min at room temperature. Chloromethyl pivalate
(30 mmol) was added and the mixture was stirred at 70 ꢁC
for 5 h. After cooling to room temperature, another 3 mmol
of triethylamine and 5 mmol of chloromethyl pivalate were
added and the mixture was stirred at room temperature over-
night. Diethyl ether (100 mL) was added and the solution
was successively washed with water (50 mL), saturated
NaHCO3 solution (2 ꢂ 50 mL) and again with water
(50 mL). The organic layer was dried over MgSO4 and the sol-
vent was removed under reduced pressure. The resulting pale
yellow oils were purified by column chromatography on silica
gel with Et2O as an eluent to give [3-(acyl-benzyloxy-amino)-
1-arylmethyl-propyl]-(2,2-dimethyl-propionyloxymethoxy)-
phosphinoyloxymethyl esters 6, 7.
6.1.5.3. 2,2-Dimethyl-propionic acid [3-(benzyloxy-formyl-
amino)-1-(3,4-dichloro-benzyl)-propyl]-(2,2-dimethyl-propio-
nyloxymethoxy)-phosphinoyloxymethyl ester (6c). Yield: 48%.
1H NMR (DMSO-d6), d (ppm): 1.15, 1.16 (2s, 18H, C(CH3)3),
1.53e1.91 (m, 2H, CH2), 2.31e2.43 (m, 1H, CH ), 2.58e3.08
(m, 2H, CH2), 3.47e3.81 (m, 2H, CH2), 4.58e4.88 (m, 2H,
PhCH2O), 5.52e5.68 (m, 4H, OCH2O), 7.17e7.61 (m, 8H, ar-
omat.), 7.79e8.25 (m, 1H, formyl.). 13C NMR (DMSO-d6),
d (ppm): 25.0 (CH2), 26.9 (C(CH3)3), 33.4 (CH2), 35.8 (d,
J ¼ 138.4 Hz, PCH), 38.8 (C(CH3)3), 42.0 (NCH2), 77.6
(PhCH2O), 81.6 (m, OCH2O), 128.5, 128.8, 129.1, 129.4,
130.5, 131.0 (tert., aromat.), 132.6, 134.1, 138.3 (quart., aro-
mat.), 162.9 (C]O, hydroxamate), 176.9 (C]O, ester). IR:
1747 cmꢀ1 (C]O, ester), 1676 cmꢀ1 (C]O, hydroxamate),
1259 cmꢀ1 (P]O). Anal. Calcd for C30H40Cl2NO9P: calcu-
lated C 54.55%, H 6.10%, N 2.12%; found C 54.61%, H
6.25%, N 1.95%.
6.1.5.1. 2,2-Dimethyl-propionic acid [1-benzyl-3-(benzyloxy-
formyl-amino)-propyl]-(2,2-dimethyl-propionyloxymethoxy)-
phosphinoyloxymethyl ester (6a). Yield: 62%. 1H NMR
(DMSO-d6), d (ppm): 1.16 (s, 18H, C(CH3)3), 1.55e1.87
(m, 2H, CH2), 2.25e2.42 (m, 1H, CH ), 2.56e2.67 (m, 1H,
CH2), 2.94e3.06 (m, 1H, CH2), 3.41e3.74 (m, 2H, CH2),
4.74 (s, 2H, PhCH2O), 5.55e5.66 (m, 4H, OCH2O), 7.18e
7.40 (m, 10H, aromat.), 7.71e8.20 (m, 1H, formyl.). 13C
NMR (CDCl3), d (ppm): 25.0 (d, JC,P ¼ 4.1 Hz, CH2), 26.9
(C(CH3)3), 34.3 (d, JC,P ¼ 3.1 Hz, CH2), 36.1 (d,
JC,P ¼ 139.4 Hz, PCH), 38.8 (C(CH3)3), 42.2 (NCH2), 76.2
(PhCH2O), 81.5, 81.6 (2d, JC,P ¼ 8.1 Hz, JC,P ¼ 7.1 Hz,
OCH2O), 126.9, 128.7, 129.1, 129.4 (tert., aromat.), 134.2
(quart., aromat.), 138.1 (d, JC,P ¼ 17.3 Hz, CH2C quart., aro-
mat.), 162.8 (C]O, hydroxamate), 176.9 (C]O, ester). IR:
1753 cmꢀ1 (C]O, ester), 1680 cmꢀ1 (C]O, hydroxamate),
1260 cmꢀ1 (P]O). Anal. Calcd for C30H42NO9P: calculated
6.1.5.4. 2,2-Dimethyl-propionic acid [3-(benzyloxy-formyl-
amino)-1-(4-methoxy-benzyl)-propyl]-(2,2-dimethyl-propiony-
loxymethoxy)-phosphinoyloxymethyl ester (6d). Yield: 34%.
1H NMR (DMSO-d6), d (ppm): 1.15, 1.16 (2s, 18H, C(CH3)3),
1.50e1.88 (m, 2H, CH2), 2.19e2.36 (m, 1H, CH ), 2.52e2.63
(m, 1H, CH2), 2.83e3.07 (m, 1H, CH2), 3.39e3.61 (m, 5H,
OCH3 overlapping CH2), 4.54e4.80 (m, 2H, PhCH2O), 5.49e
5.73 (m, 4H, OCH2O), 6.79e6.86 (m, 2H, aromat.), 7.04e
7.45 (m, 7H, aromat.), 7.73e8.23 (m, 1H, formyl.). 13C NMR
(DMSO-d6), d (ppm): 24.5 (CH2), 26.8 (C(CH3)3), 32.7 (d,
JC,P ¼ 1.8 Hz, CH2), 34.0 (d, JC,P ¼ 137.1 Hz, PCH), 38.6
(C(CH3)3), 41.6 (NCH2), 55.3 (OCH3), 77.2 (PhCH2O), 81.7
(OCH2O), 114.2 (OCCH tert., aromat.), 128.7, 129.1, 129.9,
130.3 (tert., aromat.), 130.2, 130.4 (quart., aromat.), 158.3
(CH3OC quart., aromat.), 162.1 (C]O, hydroxamate), 176.6
(C]O, ester). IR: 1753 cmꢀ1 (C]O, ester), 1668 cmꢀ1

K. Schlu¨ter et al. / European Journal of Medicinal Chemistry 41 (2006) 1385e1397
1393
(C]O, hydroxamate), 1242 cmꢀ1 (P]O). Anal. Calcd for
C31H44NO10P: calculated C 59.89%, H 7.13%, N 2.25%; found
C 59.53%, H 7.27%, N 2.19%.
hydroxamate), 176.9 (C]O, ester). IR: 1753 cmꢀ1 (C]O, es-
ter), 1667 cmꢀ1 (C]O, hydroxamate), 1260 cmꢀ1 (P]O).
Anal. Calcd for C31H44NO9P: calculated C 61.48%, H
7.32%, N 2.31%; found C 61.42%, H 7.39%, N 2.52%.
6.1.5.5. 2,2-Dimethyl-propionic acid [3-(benzyloxy-formyl-
amino)-1-(naphthalene-2-yl-methyl)-propyl]-(2,2-dimethyl-pro-
pionyloxymethoxy)-phosphinoyloxymethyl ester (6e). Yield:
35%. 1H NMR (DMSO-d6), d (ppm): 1.16 (2d, 18H, C(CH3)3),
1.63e1.93 (m, 2H, CH2), 2.40e2.49 (m, 1H, CH ), 2.72e2.91
(m, 1H, CH2), 3.07e3.26 (m, 1H, CH2), 3.51e3.79 (m, 2H,
CH2), 4.54e4.73 (m, 2H, PhCH2O), 5.52e5.76 (m, 4H,
OCH2O), 7.00e7.54 (m, 8H, aromat.), 7.74e7.91 (m, 4H, aro-
mat.), 7.93e8.29 (m, 1H, formyl.). 13C NMR (DMSO-d6),
d (ppm): 24.3 (CH2), 26.8 (C(CH3)3), 33.8 (CH2), 34.6 (d,
JC,P ¼ 140.0 Hz, PCH), 38.8 (C(CH3)3), 41.1 (NCH2), 76.4
(PhCH2O), 81.4 (OCH2O), 125.5, 126.1, 127.1, 127.3, 127.5,
127.9, 128.2, 128.6, 129.2 (tert., aromat.), 131.8, 132.9, 134.3
(quart., aromat.), 135.7(d, JC,P ¼ 14.1 Hz, CH2Cquart., aromat.),
162.5 (C]O, hydroxamate), 176.1 (C]O, ester). IR: 1753 cmꢀ1
(C]O, ester), 1679 cmꢀ1 (C]O, hydroxamate), 1263 cmꢀ1
(P]O). Anal. Calcd for C34H44NO9P: calculated C 63.64%, H
6.91%, N 2.18%; found C 63.98%, H 7.24%, N 2.03%.
6.1.5.8. 2,2-Dimethyl-propionic acid [3-(acetyl-benzyloxy-
amino)-1-(2,5-dimethyl-benzyl)-propyl]-(2,2-dimethyl-propio-
nyloxymethoxy)-phosphinoyloxymethyl ester (7b). Yield: 48%.
1H NMR (DMSO-d6), d (ppm): 1.16 (2s, 18H, C(CH3)3),
1.62e1.85 (m, 2H, CH2), 1.89 (s, 3H, acetyl. CH3), 2.17
(s, 6H, PhCH3), 2.21e2.32 (m, 1H, CH ), 2.41e2.48 (m,
1H, CH2), 2.90e3.00 (m, 1H, CH2), 3.44e3.54 (m, 1H,
CH2), 3.59e3.69 (m, 1H, CH2), 4.69 (s, 2H, PhCH2O),
5.55e5.67 (m, 4H, OCH2O), 6.87e7.06 (m, 3H, aromat.),
7.24e7.43 (m, 5H, aromat.). 13C NMR (DMSO-d6),
d (ppm): 18.8, 20.9 (2s, PhCH3), 20.6 (acetyl. CH3), 24.8
(CH2), 26.8 (C(CH3)3), 31.4 (d, JC,P ¼ 3.0 Hz, CH2), 34.1
(d, JC,P ¼ 136.7 Hz, PCH), 38.6 (C(CH3)3), 43.0 (NCH2),
75.5 (PhCH2O), 81.8 (OCH2O), 127.6, 128.8, 129.0,
129.5, 130.6, 130.7 (tert., aromat.), 133.1, 135.0 (quart., ar-
omat.), 136.5 (d, JC,P ¼ 13.9 Hz, CH2C quart., aromat.),
172.1 (C]O, hydroxamate), 176.5 (C]O, ester). IR:
1753 cmꢀ1 (C]O, ester), 1668 cmꢀ1 (C]O, hydroxamate),
1257 cmꢀ1 (P]O). Anal. Calcd for C33H48NO9P: calculated
C 62.55%, H 7.63%, N 2.21%; found C 62.40%, H 7.76%,
N 2.11%.
6.1.5.6. 2,2-Dimethyl-propionic acid [3-(benzyloxy-formyl-
amino)-1-(naphthalene-1-yl-methyl)-propyl]-(2,2-dimethyl-
propionyloxymethoxy)-phosphinoyloxymethyl ester (6f). Yield:
1
31%. H NMR (DMSO-d6), d (ppm): 1.15, 1.17 (2s, 18H,
C(CH3)3), 1.85e1.95 (m, 2H, CH2), 2.25e2.44 (m, 1H, CH ),
2.83e3.00 (m, 1H, CH2), 3.34e3.69 (m, 3H, CH2), 4.39e4.72
(m, 2H, PhCH2O), 5.53e5.81 (m, 4H, OCH2O), 7.04e7.59
(m, 9H, aromat.), 7.73e8.17 (m, 4H, aromat. overlapping for-
myl.). 13C NMR (DMSO-d6), d (ppm): 25.6 (CH2), 26.8
(C(CH3)3), 31.4 (CH2), 34.7 (d, JC,P ¼ 138.1 Hz, PCH), 38.6
(C(CH3)3), 41.8 (NCH2), 75.2 (PhCH2O), 81.9 (OCH2O),
123.5, 125.3, 125.7, 126.2, 126.8, 127.9, 128.1, 128.7, 129.3
(tert., aromat.), 131.5, 133.9, 134.3 (quart., aromat.), 162.7
(C]O, hydroxamate), 176.6 (C]O, ester). IR: 1757 cmꢀ1
(C]O, ester), 1683 cmꢀ1 (C]O, hydroxamate), 1256 cmꢀ1
(P]O). Anal. Calcd for C34H44NO9P: calculated C 63.64%,
H 6.91%, N 2.18%; found C 63.70%, H 7.12%, N 2.21%.
6.1.5.9. 2,2-Dimethyl-propionic acid [3-(acetyl-benzyloxy-
amino)-1-(3,4-dichloro-benzyl)-propyl]-(2,2-dimethyl-propio-
nyloxymethoxy)-phosphinoyloxymethyl ester (7c). Yield: 48%.
1H NMR (CDCl3), d (ppm): 1.22 (s, 18H, C(CH3)3), 1.71e
1.85 (m, 1H, CH2), 1.88e1.99 (m, 1H, CH2), 2.01 (s, 3H,
acetyl. CH3), 2.14e2.27 (m, 1H, CH ), 2.56e2.64 (m, 1H,
CH2), 3.01e3.07 (m, 1H, CH2), 3.62e3.82 (m, 2H, CH2),
4.73 (s, 2H, PhCH2O), 5.60e5.72 (m, 4H OCH2O), 6.98e
7.05 (m, 1H, aromat.), 7.27e7.40 (m, 7H, aromat.). 13C
NMR (CDCl3), d (ppm): 20.8 (acetyl. CH3), 25.4 (d,
JC,P ¼ 3.3 Hz, CH2), 27.3 (C(CH3)3), 33.8 (d, JC,P ¼ 2.3 Hz,
CH2), 36.2 (d, JC,P ¼ 140.1 Hz, PCH), 39.2 (C(CH3)3), 43.6
(NCH2), 76.7 (PhCH2O), 81.5, 81.6 (2d, JC,P ¼ 10.0 Hz,
JC,P ¼ 9.2 Hz, OCH2O), 129.0, 129.2, 129.4, 129.6, 130.9,
131.3 (tert., aromat.), 131.2, 132.9, 134.7 (quart., aromat.),
139.1 (d, JC,P ¼ 14.7 Hz, CH2C quart., aromat.), 172.2
(C]O, hydroxamate), 177.3 (C]O, ester). IR: 1753 cmꢀ1
6.1.5.7. 2,2-Dimethyl-propionic acid [3-(acetyl-benzyloxy-
amino)-1-benzyl-propyl]-(2,2-dimethyl-propionyloxymethoxy)-
phosphinoyloxymethyl ester (7a). Yield: 82%. MP: 50.2 ꢁC.
1H NMR (DMSO-d6), d (ppm): 1.15, 1.16 (2s, 18H,
C(CH3)3), 1.58e1.86 (m, 2H, CH2), 1.92 (s, 3H, acetyl.
CH3), 2.27e2.41 (m, 1H, CH ), 2.56e2.64 (m, 1H, CH2),
2.95e3.03 (m, 1H, CH2), 3.47e3.55 (m, 1H, CH2), 3.65e
3.76 (m, 1H, CH2), 4.72 (s, 2H, PhCH2O), 5.54e5.65 (m,
4H, OCH2O), 7.19e7.34 (m, 7H, aromat.), 7.36e7.41 (m,
3H, aromat.). 13C NMR (CDCl3), d (ppm): 20.4 (acetyl.
CH3), 24.9 (d, JC,P ¼ 3.1 Hz CH2), 26.9 (C(CH3)3), 34.2 (d,
JC,P ¼ 3.1 Hz, CH2), 36.1 (d, JC,P ¼ 139.4 Hz, PCH), 38.7
(C(CH3)3), 43.5 (NCH2), 76.1 (PhCH2O), 81.5, 81.6 (2d,
JC,P ¼ 6.1 Hz, OCH2O), 126.7, 128.6, 128.7, 128.9, 129.1,
129.2 (tert., aromat.), 134.4 (quart., aromat.), 138.3 (d,
JC,P ¼ 14.2 Hz, CH2C quart., aromat.), 172.1 (C]O,
(C]O,
ester),
1666 cmꢀ1
(C]O,
hydroxamate),
1259 cmꢀ1 (P]O). Anal. Calcd for C31H42Cl2NO9P: calcu-
lated C 55.20%, H 6.28%, N 2.08%; found C 55.36%, H
6.59%, N 2.01%.
6.1.5.10. 2,2-Dimethyl-propionic acid [3-(acetyl-benzyloxy-
amino)-1-(4-methoxy-benzyl)-propyl]-(2,2-dimethyl-propiony-
loxymethoxy)-phosphinoyloxymethyl ester (7d). Yield: 40%.
MP: 42.9 ꢁC. 1H NMR (CDCl3), d (ppm): 1.20, 1.21 (2s, 18H,
C(CH3)3), 1.72e1.96 (m, 2H, CH2), 1.98 (s, 3H, acetyl. CH3),
2.13e2.30 (m, 1H, CH ), 2.47e2.62 (m, 1H, CH2), 2.99e3.13
(m, 1H, CH2), 3.51e3.82 (m, 5H, OCH3 overlapping CH2),
4.67 (s, 2H, PhCH2O), 5.56e5.73 (m, 4H, OCH2O), 6.75e6.83

1394
K. Schlu¨ter et al. / European Journal of Medicinal Chemistry 41 (2006) 1385e1397
(m, 2H, aromat.), 7.03e7.14 (m, 2H, aromat.), 7.26e7.38 (m,
5H, aromat.). 13C NMR (CDCl3), d (ppm): 20.9 (acetyl. CH3),
25.2 (d, JC,P ¼ 3.1 Hz, CH2), 27.3 (C(CH3)3), 33.7 (d,
JC,P ¼ 2.5 Hz, CH2), 36.7 (d, JC,P ¼ 136.3 Hz, PCH), 39.2
(C(CH3)3), 43.8 (NCH2), 55.6 (OCH3), 76.6 (PhCH2O), 81.4
(OCH2O), 114.4 (OCCH tert., aromat.), 129.1, 129.3, 129.6,
130.5 (tert., aromat.), 130.7, 134.4 (quart., aromat.), 158.8
(CH3OC quart., aromat.), 172.0 (C]O, hydroxamate), 177.3
(C]O, ester). IR: 1749 cmꢀ1 (C]O, ester), 1664 cmꢀ1
(C]O, hydroxamate), 1246 cmꢀ1 (P]O). Anal. Calcd for
C32H46NO10P: calculated C 60.46%, H 7.29%, N 2.20%; found
C 60.54%, H 7.43%, N 2.11%.
6.1.6. General procedure for the preparation of
2,2-dimethyl-propionic acid [3-(acyl-hydroxy-amino)-
1-arylmethyl-propyl]-(2,2-dimethyl-propionyloxymethoxy)-
phosphinoyloxymethyl esters 8aef, 9aef
The appropriate O-protected hydroxamic acids 6aef, 7aef
(1 mmol) were dissolved in freshly distilled methanol
(50 mL). After addition of the PdeC catalyst, hydrogen gas
was added and the mixture was hydrogenated for 2 h, except
for compounds 6e,f and 7e,f which required a reaction time
of 14 h in order to obtain the pure tetrahydronaphthyl deriva-
tives. In case of hydroxamic acids 8,9c ethyl acetate was used
as solvent. The suspension was filtrated through an SPE tube
RP-18 purchased from Supelco. The filtrate was evaporated
to give 2,2-dimethyl-propionic acid [3-(acyl-hydroxyamino)-
1-arylmethylpropyl]-(2,2-dimethyl-propionyloxymethoxy)-ph
osphinoyloxymethyl esters 8aef, 9aef as pale yellow oils.
6.1.5.11. 2,2-Dimethyl-propionic acid [3-(acetyl-benzyloxy-
amino)-1-(naphthalene-2-yl-methyl)-propyl]-(2,2-dimethyl-
propionyloxymethoxy)-phosphinoyloxymethyl
ester
(7e).
1
Yield: 35%. MP: 60.6 ꢁC. H NMR (CDCl3), d (ppm): 1.15,
1.16 (2s, 18H, C(CH3)3), 1.60e1.85 (m, 2H, CH2), 1.88 (s,
3H, acetyl. CH3), 2.41e2.48 (m, 1H, CH ), 2.71e2.87 (m,
1H, CH2), 3.10e3.25 (m, 1H, CH2), 3.49e3.63 (m, 1H,
CH2), 3.68e3.81 (m, 1H, CH2), 4.66 (s, 2H, PhCH2O),
5.57e5.71 (m, 4H, OCH2O), 7.07e7.54 (m, 8H, aromat.),
7.71e7.93 (m, 4H, aromat.). 13C NMR (CDCl3), d (ppm):
20.6 (acetyl. CH3), 24.7 (d, JC,P ¼ 3.9 Hz, CH2), 26.8
6.1.6.1. 2,2-Dimethyl-propionic acid [1-benzyl-3-(formyl-
hydroxyamino)-propyl]-(2,2-dimethyl-propionyloxymethoxy)-
phosphinoyloxymethyl ester (8a). Yield: 99%. 1H NMR
(DMSO-d6), d (ppm): 1.16, 1.17 (2s, 18H, C(CH3)3), 1.54e
1.87 (m, 2H, CH2), 2.25e2.42 (m, 1H, CH2), 2.57e2.69 (m,
1H, CH2), 2.92e3.04 (m, 1H, CH2), 3.38e3.63 (m, 2H,
CH2), 5.51e5.65 (m, 4H, OCH2O), 7.20e7.33 (m, 5H, aro-
mat.), 7.73 (s, 0.5H, formyl.), 8.15 (s, 0.5H, formyl.), 9.48
(s, 0.5H, OH ), 9.92 (s, 0.5H, OH ). 13C NMR (CDCl3),
(C(CH3)3), 33.8 (d, JC,P ¼ 1.9 Hz, CH2), 35.1 (d, JC,P
¼
136.7 Hz, PCH), 38.6 (C(CH3)3), 43.0 (d, JC,P ¼ 14.9 Hz,
NCH2), 75.6 (PhCH2O), 81.8 (OCH2O), 126.0, 126.5, 127.5,
127.7, 127.8, 127.9, 128.3, 128.7, 128.9, 129.6 (tert., aromat.),
132.2, 133.4, 134.9 (quart., aromat.), 136.2 (d, JC,P ¼ 15.4 Hz,
CH2C quart., aromat.), 172.5 (C]O, hydroxamate), 176.5
(C]O, ester). IR: 1753 cmꢀ1 (C]O, ester), 1663 cmꢀ1
(C]O, hydroxamate), 1258 cmꢀ1 (P]O). Anal. Calcd for
C35H46NO9P: calculated C 64.11%, H 7.07%, N 2.14%; found
C 64.48%, H 7.30%, N 2.04%.
d
(ppm): 23.3, 25.1 (2d, JC,P ¼ 3.1 Hz, CH2), 26.9
(C(CH3)3), 34.5, 34.6 (2d, JC,P ¼ 4.1 Hz, JC,P ¼ 3.1 Hz,
CH2), 35.5 (d, JC,P ¼ 137.3 Hz, PCH), 38.8 (C(CH3)3), 45.1,
47.2 (2d, JC,P ¼ 4.1 Hz, JC,P ¼ 5.1 Hz, NCH2), 81.5, 81.9
(2d, JC,P ¼ 7.1 Hz, OCH2O), 127.0, 128.8, 128.9 (tert., aro-
mat.), 137.4, 138.0 (2d, JC,P ¼ 16.3 Hz, CH2C quart., aromat.),
156.2, 163.6 (C]O, hydroxamate), 176.8, 177.0 (C]O, es-
ter). IR: 3205 cmꢀ1 (OeH), 1753 cmꢀ1 (C]O, ester),
1673 cmꢀ1 (C]O, hydroxamate), 1256 cmꢀ1 (P]O). Anal.
Calcd for C23H36NO9P: calculated C 55.08%, H 7.24%, N
2.79%; found C 54.52%, H 6.96%, N 2.72%.
6.1.5.12. 2,2-Dimethyl-propionic acid [3-(acetyl-benzyloxy-
amino)-1-(naphthalene-1-yl-methyl)-propyl]-(2,2-dimethyl-
propionyloxymethoxy)-phosphinoyloxymethyl ester (7f). Yield:
52%. 1H NMR (CDCl3), d (ppm): 1.22, 1.24 (2s, 18H,
C(CH3)3), 1.76 (s, 3H, acetyl. CH3), 1.82e2.07 (m, 2H,
CH2), 2.35e2.49 (m, 1H, CH ), 2.81e2.96 (m, 1H, CH2),
3.42e3.84 (m, 3H, CH2), 4.48 (s, 2H, PhCH2O), 5.66e5.82
(m, 4H, OCH2O), 7.10e7.21 (m, 2H, aromat.), 7.29e7.40
(m, 5H, aromat.), 7.44e7.57 (m, 2H, aromat.), 7.70e8.00
(m, 3H, aromat.). 13C NMR (CDCl3), d (ppm): 20.6 (acetyl.
CH3), 25.8 (d, JC,P ¼ 2.8 Hz, CH2), 27.3 (C(CH3)3), 32.4
(d, JC,P ¼ 2.2 Hz, CH2), 35.3 (d, JC,P ¼ 139.3 Hz, PCH),
39.2 (C(CH3)3), 44.0 (d, JC,P ¼ 15.1 Hz, NCH2), 76.3
(PhCH2O), 82.1 (OCH2O), 123.9, 125.7, 126.2, 126.9,
128.2, 128.3, 129.0, 129.2, 129.4, 129.5 (tert., aromat.),
132.0, 134.4, 134.5, 134.6 (quart., aromat.), 172.0 (C]O,
hydroxamate), 177.3 (C]O, ester). IR: 1753 cmꢀ1 (C]O,
ester), 1666 cmꢀ1 (C]O, hydroxamate), 1255 cmꢀ1
6.1.6.2. 2,2-Dimethyl-propionic acid [1-(2,5-dimethyl-benzyl)-
3-(formyl-hydroxy-amino)-propyl]-(2,2-dimethyl-propionylox-
ymethoxy)-phosphinoyloxymethyl ester (8b). Yield: 92%. H
1
NMR (CDCl3), d (ppm): 1.19, 1.20 (2s, 18H, C(CH3)3),
1.57e1.93 (m, 2H, CH2), 2.14e2.35 (m, 7H, PhCH3 overlap-
ping CH ), 2.90e3.04 (m, 1H, CH2), 3.26e3.63 (m, 3H, CH2),
5.51e5.70 (m, 4H, OCH2O), 6.88e7.13 (m, 3H, aromat.),
7.66e8.18 (m, 1H, formyl.), 9.45e9.99 (m, 1H, OH ). 13C
NMR (CDCl3), d (ppm): 18.9, 20.9 (PhCH3), 26.1, 27.8 (2d,
JC,P ¼ 3.5 Hz, JC,P ¼ 4.1 Hz, CH2), 26.8 (C(CH3)3), 31.4,
31.5 (2d, JC,P ¼ 2.4 Hz, JC,P ¼ 2.9 Hz, CH2), 33.3, 33.4 (2d,
JC,P ¼ 136.2 Hz, JC,P ¼ 137.1 Hz, PCH), 38.6 (C(CH3)3),
44.4, 47.5 (2d, JC,P ¼ 6.9 Hz, NCH2), 81.8 (OCH2O), 127.6,
130.6, 130.7 (tert., aromat.), 133.1, 135.0 (quart., aromat.),
136.7 (d, JC,P ¼ 14.5 Hz, CH2C quart., aromat.), 157.2,
161.1, 161.9 (C]O, hydroxamate), 176.5 (C]O, ester). IR:
3205 cmꢀ1 (OeH), 1752 cmꢀ1 (C]O, ester), 1674 cmꢀ1
(C]O, hydroxamate), 1246 cmꢀ1 (P]O). Anal. Calcd for
(P]O). Anal. Calcd for C35H46NO9P: calculated
C
64.11%, H 7.07%, N 2.14%; found C 63.92%, H 7.39%, N
2.15%.

K. Schlu¨ter et al. / European Journal of Medicinal Chemistry 41 (2006) 1385e1397
1395
C25H40NO9P: calculated C 56.70%, H 7.61%, N 2.64%; found
C 56.46%, H 7.51%, N 2.57%.
C 58.37%, H 7.62%, N 2.52%; found C 58.73%, H 7.96%,
N 2.53%.
6.1.6.6. 2,2-Dimethyl-propionic acid [3-(formyl-hydroxy-
amino)-1-(5,6,7,8-tetrahydronaphthalene-1-yl-methyl)-propyl]-
(2,2-dimethyl-propionyloxymethoxy)-phosphinoyloxymethyl
ester (8f). Yield: 91%. 1H NMR (CDCl3), d (ppm): 1.17e1.28
(m, 18H, C(CH3)3), 1.53e2.40 (m, 8H, CH, CH2), 2.50e2.85
(m, 4H, CH2), 3.00e3.65 (m, 3H, CH2), 5.57e5.78 (m, 4H,
OCH2O), 6.84e7.15 (m, 3H, aromat.), 7.54e8.46 (m, 1H, for-
myl.). 13C NMR (CDCl3), d (ppm): 22.7, 23.3 (CH2), 25.6
(JC,P ¼ 4.2 Hz, CH2), 26.9 (C(CH3)3), 30.0, 31.4, 36.4
(CH2), 33.3 (d, JC,P ¼ 136.2 Hz, PCH), 38.8 (C(CH3)3), 45.3
(NCH2), 80.0 (m, OCH2O), 125.4, 127.3, 128.4 (tert., aro-
mat.), 135.5 (quart., aromat.), 138.1 (d, JC,P ¼ 12.4 Hz,
CH2C quart., aromat.), 156.0, 161.2, 163.5 (C]O, hydroxa-
mate), 176.9 (C]O, ester). IR: 3199 cmꢀ1 (OeH),
1755 cmꢀ1 (C]O, ester), 1670 cmꢀ1 (C]O, hydroxamate),
1240 cmꢀ1 (P]O). Anal. Calcd for C27H42NO9P: calculated
C 58.37%, H 7.62%, N 2.52%; found C 58.41%, H 7.74%,
N 2.50%.
6.1.6.3. 2,2-Dimethyl-propionic acid [1-(3,4-dichloro-benzyl)-
3-(formyl-hydroxy-amino)-propyl]-(2,2-dimethyl-propionylox-
ymethoxy)-phosphinoyloxymethyl ester (8c). Yield: 88%. 1H
NMR (CDCl3), d (ppm): 1.23e1.26 (m, 18H, C(CH3)3),
1.84e2.34 (m, 3H, CH, CH2), 2.49e2.66 (m, 1H, CH2),
2.95e3.14 (m, 1H, CH2), 3.30e3.76 (m, 2H, CH2), 5.54e
5.76 (m, 4H, OCH2O), 6.98e7.42 (m, 3H, aromat.), 7.81e
8.46 (m, 1H, formyl.). 13C NMR (CDCl3), d (ppm): 23.6,
25.0 (2s, CH2), 26.9 (C(CH3)3), 33.7 (CH2), 35.2 (d,
JC,P ¼ 138.8 Hz, PCH), 38.8 (C(CH3)3), 44.8, 46.9 (NCH2),
127.5, 130.8, 131.0 (tert., aromat.), 132.7, 137.9, 142.9 (quart.,
aromat.), 156.5, 163.7 (C]O, hydroxamate), 163.7, 176.9,
177.1 (C]O, ester). IR: 3207 cmꢀ1 (OeH), 1749 cmꢀ1
(C]O, ester), 1670 cmꢀ1 (C]O, hydroxamate), 1256 cmꢀ1
(P]O). HRFAB-MS C23H34Cl2NO9P [M þ H]þ: calculated
570.1428; found 570.1444.
6.1.6.4. 2,2-Dimethyl-propionic acid [3-(formyl-hydroxy-
amino)-1-(4-methoxy-benzyl)-propyl]-(2,2-dimethyl-propiony-
loxymethoxy)-phosphinoyloxymethyl ester (8d). Yield: 92%.
1H NMR (CDCl3), d (ppm): 1.20e1.28 (m, 18H, C(CH3)3),
1.60e2.32 (m, 3H, CH2, CH ), 2.43e2.63 (m, 1H, CH2),
2.97e3.71 (m, 3H, CH2), 3.79 (s, 3H, OCH3), 5.56e5.78
(m, 4H, OCH2O), 6.78e6.90 (m, 2H, aromat.), 7.01e7.16
(m, 2H, aromat.), 7.64e8.49 (m, 1H, formyl.). 13C NMR
(CDCl3), d (ppm): 23.6, 25.3 (2d, JC,P ¼ 2.3 Hz), 27.3
(C(CH3)3), 34.0, 34.1 (2d, JC,P ¼ 3.9 Hz, JC,P ¼ 2.3 Hz,
CH2), 35.6, 36.0 (2d, JC,P ¼ 137.6 Hz, JC,P ¼ 136.4 Hz,
PCH), 39.2 (C(CH3)3), 45.5, 47.6 (2d, JC,P ¼ 3.6 Hz,
JC,P ¼ 6.0 Hz, NCH2), 55.7 (OCH3), 81.9 (OCH2O), 114.6
(OCCH tert., aromat.), 130.3 (tert., aromat.), 129.6 (d,
JC,P ¼ 17.7 Hz, CH2C quart., aromat.), 158.9 (CH3OC quart.,
aromat.), 156.5, 161.7, 164.0 (C]O, hydroxamate), 177.4
(C]O, ester). IR: 3219 cmꢀ1 (OeH), 1753 cmꢀ1 (C]O, es-
ter), 1666 cmꢀ1 (C]O, hydroxamate), 1247 cmꢀ1 (P]O).
Anal. Calcd for C24H38NO10P: calculated C 54.23%, H
7.21%, N 2.64%; found C 54.37%, H 7.08%, N 2.74%.
6.1.6.7. 2,2-Dimethyl-propionic acid [3-(acetyl-hydroxy-
amino)-1-benzyl-propyl]-(2,2-dimethyl-propionyloxymethoxy)-
phosphinoyloxymethyl ester (9a). Yield: 99%. 1H NMR
(DMSO-d6), d (ppm): 1.16, 1.17 (2s, 18H, C(CH3)3), 1.53e
1.67 (m, 1H, CH2), 1.72e1.93 (m, 4H, acetyl. CH3 overlap-
ping CH2), 2.26e2.40 (m, 1H, CH ), 2.56e2.68 (m, 1H,
CH2), 2.91e3.02 (m, 1H, CH2), 3.36e3.43 (m, 1H, CH2),
3.55e3.65 (m, 1H, CH2), 5.50e5.63 (m, 4H, OCH2O),
7.19e7.33 (m, 5H, aromat.), 9.66 (s, 1H, OH ). 13C NMR
(CDCl3), d (ppm): 20.6 (acetyl. CH3), 23.6 (JC,P ¼ 2.0 Hz,
CH2), 26.9 (C(CH3)3), 34.5 (d, JC,P ¼ 4.1 Hz, CH2), 35.4 (d,
JC,P ¼ 137.3 Hz, PCH), 38.8 (C(CH3)3), 46.0 (NCH2), 81.6,
81.8 (2d, JC,P ¼ 8.1 Hz, JC,P ¼ 6.1 Hz, OCH2O), 126.9,
128.8, 128.9 (tert., aromat.), 137.5 (d, JC,P ¼ 17.3 Hz, CH2C
quart., aromat.), 172.8 (C]O, hydroxamate), 176.8, 176.9
(C]O, ester). IR: 3195 cmꢀ1 (OeH), 1754 cmꢀ1 (C]O, es-
ter), 1622 cmꢀ1 (C]O, hydroxamate), 1233 cmꢀ1 (P]O).
Anal. Calcd for C24H38NO9P: calculated C 55.92%, H
7.43%, N 2.72%; found C 55.61%, H 7.47%, N 2.61%.
6.1.6.5. 2,2-Dimethyl-propionic acid [3-(formyl-hydroxy-amino)-
1-(5,6,7,8-tetrahydronaphthalene-2-yl-methyl)-propyl]-(2,2-
dimethyl-propionyloxymethoxy)-phosphinoyloxymethyl ester
(8e). Yield: 92%. 1H NMR (CDCl3), d (ppm): 1.24, 1.25
(2s, 18H, C(CH3)3, 1.40e2.54 (m, 8H, CH2, CH ), 2.59e
2.92 (m, 4H, CH2), 2.99e3.55 (m, 3H, CH2), 5.59e5.82 (m,
4H, OCH2O), 6.73e7.13 (m, 3H, aromat.), 7.90e8.24 (m,
1H, formyl.). 13C NMR (CDCl3), d (ppm): 23.1 (d,
JC,P ¼ 4.3 Hz, CH2), 26.9 (C(CH3)3), 27.1, 27.2 (CH2), 29.0,
29.4 (CH2), 31.3 (d, JC,P ¼ 143.8 Hz, PCH), 36.1 (CH2),
38.8 (C(CH3)3), 81.5 (OCH2O), 129.4, 129.6 (tert., aromat.),
133.9, 135.7, 138.7 (quart., aromat.), 161.2 (C]O, hydroxa-
mate), 177.9 (C]O, ester). IR: 3292 cmꢀ1 (OeH),
1753 cmꢀ1 (C]O, ester), 1679 cmꢀ1 (C]O, hydroxamate),
1263 cmꢀ1 (P]O). Anal. Calcd for C27H42NO9P: calculated
6.1.6.8. 2,2-Dimethyl-propionic acid [3-(acetyl-hydroxy-
amino)-1-(2,5-dimethyl-benzyl)-propyl]-(2,2-dimethyl-propio-
nyloxymethoxy)-phosphinoyloxymethyl ester (9b). Yield: 91%.
1H NMR (DMSO-d6), d (ppm): 1.19, 1.20 (2s, 18H, C(CH3)3),
1.59e1.87 (m, 2H, CH2), 1.90 (s, 3H, acetyl. CH3), 2.16e2.35
(m, 7H, PhCH3 overlapping CH ), 2.87e3.01 (m, 1H, CH2),
3.19e3.64 (m, 3H, CH2), 5.52e5.70 (m, 4H, OCH2O),
6.89e7.11 (m, 3H, aromat.), 9.66 (s, 1H, OH ). 13C NMR
(DMSO-d6), d (ppm): 18.9, 20.9 (2s, PhCH3), 20.6 (acetyl.
CH3), 25.1 (JC,P ¼ 2.9 Hz, CH2), 26.8 (C(CH3)3), 31.3 (d,
JC,P ¼ 4.2 Hz, CH2), 33.7 (d, JC,P ¼ 136.5 Hz, PCH), 38.6
(C(CH3)3), 45.7 (NCH2), 81.8 (OCH2O), 127.5, 130.5, 130.7
(tert., aromat.), 133.1, 135.0 (quart., aromat.), 136.7 (d,
JC,P ¼ 14.4 Hz, CH2C quart., aromat.), 171.4 (C]O, hydrox-
amate), 176.5 (C]O, ester). IR: 3195 cmꢀ1 (OeH),

1396
K. Schlu¨ter et al. / European Journal of Medicinal Chemistry 41 (2006) 1385e1397
1758 cmꢀ1 (C]O, ester), 1637 cmꢀ1 (C]O, hydroxamate),
1236 cmꢀ1 (P]O). Anal. Calcd for C26H42NO9P: calculated
C 57.45%, H 7.79%, N 2.58%; found C 57.07%, H 7.89%,
N 2.58%.
(OCH2O), 121.1, 124.6, 124.7 (tert., aromat.), 130.9, 132.7,
138.4 (quart., aromat.), 173.3 (C]O, hydroxamate), 177.4
(C]O, ester). IR: 3207 cmꢀ1 (OeH), 1753 cmꢀ1 (C]O, es-
ter), 1643 cmꢀ1 (C]O, hydroxamate), 1238 cmꢀ1 (P]O).
HRFAB-MS C28H44NO9P [M þ H]þ: calculated 570.2834;
found 570.2810.
6.1.6.9. 2,2-Dimethyl-propionic acid [3-(acetyl-hydroxy-
amino)-1-(3,4-dichloro-benzyl)-propyl]-(2,2-dimethyl-propio-
nyloxymethoxy)-phosphinoyloxymethyl ester (9c). Yield: 91%.
1H NMR (DMSO-d6), d (ppm): 1.16 (2s, 18H, C(CH3)3),
1.47e1.87 (m, 2H, CH2), 1.92 (s, 3H, acetyl. CH3), 2.26e
2.46 (m, 1H, CH ), 2.61e3.00 (m, 2H, CH2), 3.37e3.70 (m,
2H, CH2), 5.47e5.68 (m, 4H, OCH2O), 7.19e7.27 (m, 1H, ar-
omat.), 7.49e7.59 (m, 2H, aromat.), 9.69 (s, 1H, OH ). 13C
NMR (DMSO-d6), d (ppm): 20.6 (acetyl. CH3), 25.0 (CH2),
26.8 (C(CH3)3), 32.7 (d, JC,P ¼ 2.3 Hz, CH2), 36.7 (d,
JC,P ¼ 145.6 Hz, PCH), 38.6 (C(CH3)3), 45.6 (NCH2), 81.7
(OCH2O), 129.9, 130.6, 131.4 (tert., aromat.), 129.4, 131.2
(quart., aromat.), 140.2 (d, JC,P ¼ 12.2 Hz, CH2C quart., aro-
mat.), 174.7 (C]O, hydroxamate), 176.5 (C]O, ester). IR:
3190 cmꢀ1 (OeH), 1749 cmꢀ1 (C]O, ester), 1620 cmꢀ1
(C]O, hydroxamate), 1240 cmꢀ1 (P]O). HRFAB-MS
C24H36Cl2NO9P [M þ H]þ: calculated 584.1585; found
584.1587.
6.1.6.12. 2,2-Dimethyl-propionic acid [3-(acetyl-hydroxy-
amino)-1-(5,6,7,8-tetrahydronaphthalene-1-yl)-propyl]-(2,2-
dimethyl-propionyloxymethoxy)-phosphinoyloxymethyl ester
(9f). Yield: 93%. 1H NMR (CDCl3), d (ppm): 1.14e1.31
(m, 18H, C(CH3)3), 1.51e2.82 (m, 15H, acetyl. CH3 overlap-
ping CH2, CH ), 2.85e3.45 (m, 2H, CH2), 3.53e3.89 (m, 1H,
CH2), 5.56e5.79 (m, 4H, OCH2O), 6.82e7.19 (m, 3H, aro-
mat.), 9.04e9.97 (m, 1H, OH ). 13C NMR (CDCl3), d (ppm):
20.6 (acetyl. CH3), 22.7, 23.3 (CH2), 26.3 (d, JC,P ¼ 2.8 Hz,
CH2), 26.8, 26.9 (C(CH3)3), 30.0, 31.4 (CH2), 34.9 (d,
JC,P ¼ 144.8 Hz, PCH), 38.8 (C(CH3)3), 46.0, 46.3 (2s,
NCH2), 81.6 (d, JC,P ¼ 7.2 Hz, OCH2O), 125.4, 127.0, 128.3
(tert., aromat.), 135.3, 135.8, 138.1 (quart., aromat.), 172.9
(C]O, hydroxamate), 176.9 (C]O, ester). IR: 3190 cmꢀ1
(OeH), 1751 cmꢀ1 (C]O, ester), 1639 cmꢀ1 (C]O, hydrox-
amate), 1232 cmꢀ1 (P]O). Anal. Calcd for C28H44NO9P: cal-
culated C 59.04%, H 7.79%, N 2.46%; found C 59.13%, H
8.06%, N 2.30%.
6.1.6.10. 2,2-Dimethyl-propionic acid [3-(acetyl-hydroxy-
amino)-1-(4-methoxy-benzyl)-propyl]-(2,2-dimethyl-propiony-
loxymethoxy)-phosphinoyloxymethyl ester (9d). Yield: 91%.
1H NMR (CDCl3), d (ppm): 1.20e1.28 (m, 18H, C(CH3)3),
1.58e2.36 (m, 6H, acetyl. CH3 overlapping CH2, CH ),
2.42e2.60 (m, 1H, CH2), 2.91e3.36 (m, 2H, CH2), 3.53e
3.84 (m, 4H, OCH3 overlapping CH2), 5.53e5.80 (m, 4H,
OCH2O), 6.75e6.90 (m, 2H, aromat.), 7.00e7.16 (m, 2H, ar-
omat.). 13C NMR (CDCl3), d (ppm): 20.6 (acetyl. CH3), 23.5
6.2. Determination of in vitro antimalarial activity
6.2.1. Culture of P. falciparum
The P. falciparum 3D7 strain was maintained in continuous
culture, according to Trager and Jensen and Das Gupta et al.
[14b]. The parasites were grown in human red blood cells
(RBCs blood group A positive), RPMI 1640 medium supple-
mented with 25 mM HEPES, 20 mM sodium bicarbonate,
and 0.5% AlbuMAX (Invitrogen, Karlsruhe, Germany) at 5%
hematocrit. The flasks were gassed with 90% N2, 5% O2, and
5% CO2 and incubated at 37 ꢁC. The development of the cul-
tures and the percentage of infected RBCs were determined
by light microscopy of Giemsa-stained thin smears.
(d, JC,P ¼ 2.8 Hz, CH2), 26.9 (2s, C(CH3)3), 33.6 (d, JC,P
¼
3.6 Hz, CH2), 35.7 (d, JC,P ¼ 136.6 Hz, PCH), 38.8
(C(CH3)3), 46.0 (d, JC,P ¼ 3.5 Hz, NCH2), 55.3 (OCH3), 81.6
(OCH2O), 114.1 (OCCH tert., aromat.), 129.9 (tert., aromat.),
129.3 (d, JC,P ¼ 17.3 Hz, quart., aromat.), 158.5 (CH3OC
quart., aromat.), 172.8 (C]O, hydroxamate), 176.9 (C]O,
ester). IR: 3199 cmꢀ1 (OeH), 1753 cmꢀ1 (C]O, ester),
1622 cmꢀ1 (C]O, hydroxamate), 1246 cmꢀ1 (P]O). Anal.
Calcd for C25H40NO10P: calculated C 55.04%, H 7.39%, N
2.57%; found C 55.28%, H 7.44%, N 2.56%.
6.2.2. Preparation of drug solutions
Twenty micromoles of the respective compounds were
dissolved in 400 ml DMSO and further diluted with water/
ethanol (50/50) to obtain the particular concentration.
6.1.6.11. 2,2-Dimethyl-propionic acid [3-(acetyl-hydroxy-
amino)-1-(5,6,7,8-tetrahydronaphthalene-2-yl)-propyl]-(2,2-
dimethyl-propionyloxymethoxy)-phosphinoyloxymethyl ester
(9e). Yield: 78%. 1H NMR (CDCl3), d (ppm): 1.22e1.27
(m, 18H, C(CH3)3), 1.74e1.82 (m, 4H, CH2), 2.06e2.37 (m,
6H, acetyl. CH3 overlapping CH2, CH ), 2.43e2.58 (m, 1H,
CH2), 2.63e2.87 (m, 4H, CH2), 2.96e3.42 (m, 2H, CH2),
3.52e4.19 (m, 1H, CH2), 5.57e5.79 (m, 4H, OCH2O),
6.76e7.15 (m, 3H, aromat.), 8.81e9.77 (m, 1H, OH ). 13C
NMR (CDCl3), d (ppm): 20.6 (acetyl. CH3), 23.1 (d,
JC,P ¼ 4.7 Hz, CH2), 24.2, 24.5 (CH2), 26.9 (C(CH3)3), 29.1
(d, JC,P ¼ 4.7 Hz, CH2), 30.5 (d, JC,P ¼ 137.1 Hz, PCH),
32.9, 33.9 (CH2), 39.5 (C(CH3)3), 41.3 (NCH2), 81.6
6.2.3. Determination of parasite growth inhibition
The tests were carried out in 96-well microtiter plates under
strict aseptic conditions, according to literature. Dilutions of
each compound were added to 250 ml of a suspension of
P. falciparum infected erythrocytes (1.5% hematocrit, 1.5e
2% parasitemia). The plates were flushed with a gas mixture
consisting of 90% N2, 5% O2 and 5% CO2, closed tightly
and incubated at 37 ꢁC for 24 h. Afterwards, 0.1 mCi of 8-
[3H]-hypoxanthine was added to each well. The plates were
flushed with the above mentioned gas mixture, incubated for
additional 24 h at 37 ꢁC and subsequently harvested with
a cell harvester system (Inotech, Dottikon, Switzerland).

K. Schlu¨ter et al. / European Journal of Medicinal Chemistry 41 (2006) 1385e1397
1397
(b) J. Wiesner, F. Seeber, Expert. Opin. Ther. Targets
23e44.
9
(2005)
Infected erythrocytes were washed four times with distilled wa-
ter before they were analysed for incorporated radioactivity in
a multidetector liquid scintillation counter (Wallac, Turku,
Finland).
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