Diastereoselective hydrophosphonylation of imines using (R,R)-TADDOL phosphite. Asymmetric synthesis of α-aminophosphonic acid derivatives

Article abstract of DOI:10.1039/c003004j

Efficient synthesis of α-aminophosphonic acid derivatives is achieved, the key step being a diastereoselective hydrophosphonylation of N-diphenylphosphinyl imines using a readily available chiral cyclic (R,R)-TADDOL-phosphite derived from inexpensive natu

Full text of DOI:10.1039/c003004j

View Online / Journal Homepage / Table of Contents for this issue
COMMUNICATION
www.rsc.org/obc | Organic & Biomolecular Chemistry
Diastereoselective hydrophosphonylation of imines using (R,R)-TADDOL
phosphite. Asymmetric synthesis of a-aminophosphonic acid derivatives†
Francisco Palacios,* Tomasz K. Olszewski and Javier Vicario
Received 17th February 2010, Accepted 8th July 2010
DOI: 10.1039/c003004j
Efficient synthesis of a-aminophosphonic acid derivatives is
achieved, the key step being a diastereoselective hydrophos-
phonylation of N-diphenylphosphinyl imines using a readily
available chiral cyclic (R,R)-TADDOL-phosphite derived
from inexpensive natural tartaric acid.
Introduction
a-Aminophosphonic acids1 are structural analogous to a-amino
acids, obtained by isosteric substitution of the carboxylic acid by
a phosphonate moiety. As expected from this analogy the single
a-aminophosphonic acid molecules or their phosphonate esters
as well as phosphapeptides containing a-aminophosphonic units
show an assorted biological activity2 as happens of catalytic
antibodies,3a peptide mimetics,3b enzyme inhibitors,3c–e and an-
tibacterial agents.3f Moreover they are key compounds in agro-
Fig. 1 (-)-Borneol I, (-)-Menthol II, (R)-(+)-BINOL III and TADDOL
IV derived phosphites.
chemistry and have found several applications as fungicides4a or
herbicides.4b
The Pudovik reaction5 is one of the most straight methods
which avoids the presence of mixtures of diastereoisomers and
for the synthesis of a-aminophosphonic acid derivatives, which
involves a variant of Strecker reaction based in the nucleophilic ad-
dition of phosphites to imines. Because the biological activity of a-
aminophosphonic acid derivatives depends very often on the abso-
lute configuration of their a carbon, a strong effort has been made
in the study of stereoselective Pudovik reactions,6 mainly focused
in the catalytic hydrophosphonylation of imines.7 However, there
are only few examples of diastereoselective Pudovik reactions with
acyclic imines using chiral phosphites.6 Addition of (-)-bornyl
and (-)-menthyl phosphites I and II (Fig. 1) to N-benzylimine
derived from benzaldehyde has been reported to afford a-
aminophosphonates with moderate to good diastereoselectivity.8
Last years we have been involved in the synthesis of a-9 and
b-aminophosphonate10 derivatives and we even used TADDOL
phosphoimidate derivatives as catalyst for the asymmetric syn-
thesis of a-dehydroaminoester derivatives.11 In this context, we
thought12,13 that TADDOL derived phosphite14 IV (Fig. 1) would
be a suitable candidate as phosphorus nucleophile for Pudovik
reactions. (R,R)-TADDOL auxiliary is easily prepared in a simple
two step procedure from cheap natural tartaric acid15 and, unlike
natural alcohols, only one unit of chiral auxiliary relative to phos-
phorus is needed for the preparation of the hydrogenphosphonate
ester. Moreover, TADDOL phosphite derivative shows a C-2
symmetry, implying the presence of a non chiral phosphorus(V)
their separation. Furthermore, the endocyclic P–O bonds in
the 7-membered ring, now including four sp3 carbons, would
be more stable than in the case of BINOL phosphite III as
this is a less strained structure. Now, as a continuation of our
work in the field of aminophosphorus compounds we report
here a diastereoselective hydrophosphonylation of imines using
a TADDOL derived phosphite and applied to the stereoselective
synthesis of a-aminophosphonic acids.
Results and discussion
(R,R)-TADDOL derived phosphite 3 is easily synthesized by
generation of chlorophosphite 2 from (R,R)-TADDOL 1 and PCl3
and subsequent hydrolysis ‘in situ’ with triethylamine in aqueous
media (Scheme 1, 95%).
Scheme 1 Synthesis of (R,R)-TADDOL phosphite 3.
First we tested the hydrophosphonylation reaction of several
aldimines derived from benzaldehyde in THF or CH2Cl2 (Table 1).
In terms of chiral induction, it was established that the use of
diphenylphosphinylimines is preferred if compared to tosyl or
benzylamines. The larger size of diphenylphosphinyl substituent
at the nitrogen might be the reason for this behaviour. The benefits
of diphenylphosphinyl substituent on the electronic activation
Departamento de Qu´ımica Orga´nica I, Facultad de Farmacia, Universi-
dad del Pa´ıs Vasco, Apartado 450, 01080 Vitoria, Spain. E-mail: fran-
cisco.palacios@ehu.es; Fax: (+34)-945-013049; Tel: (+34) 945 183103
† Electronic supplementary information (ESI) available: Preparation and
full characterization of compounds 3, 4f–h and 5 and copies of 1H, 13C of
a-aminophosphonates 4. See DOI: 10.1039/c003004j
This journal is
The Royal Society of Chemistry 2010
Org. Biomol. Chem., 2010, 8, 4255–4258 | 4255
©

View Online
Table 1 Hydrophosphonylation of aldimines derived from benzaldehyde with (R,R)-TADDOL phosphite 3
Entry
R
Base
Solvent
T/◦C
%Conva
dra
1
2
3
4
5
6
7
8
Bz
Bz
Ts
Ts
POPh2
POPh2
POPh2
POPh2
POPh2
POPh2
POPh2
POPh2
POPh2
POPh2
LDA (1 eq.)
ZnEt2/TMEDA (1 eq.)
LDA (1 eq.)
ZnEt2/TMEDA (1 eq.)
Et3N (1 eq.)
No
No
LDA
ZnEt2 (1 eq.)
ZnEt2/TMEDA (1 eq.)
ZnEt2/TMEDA (1.2 eq.)
ZnEt2/TMEDA (1.5 eq.)
ZnEt2/TMEDA (1.8 eq.)
ZnEt2/TMEDA (2.1 eq.)
THF
THF
THF
THF
CH2Cl2
CH2Cl2
CH2Cl2
THF
THF
THF
THF
THF
THF
THF
-80
-80
-80
-80
r.t.
r.t.
40
-80
-80
-80
-80
-80
-80
-80
97
48
88
79
90
0
56 : 44
65 : 35
75 : 25
62 : 38
45 : 55
—
0
—
75
70
82
90
95
97
97
74 : 26
70 : 30
92 : 8
>95 : 5
>95 : 5
>95 : 5
>95 : 5
9
10
11
12
13
14
a Determined by 31P NMR.
Table 2 Hydrophosphonylation of N-diphenylphosphinyl aldimines with (R,R)-TADDOL phosphite 3
Entry
Comp.
R
%Yielda
31P NMR (major)
31P NMR (minor)
drb
1
2
3
4
5
6
7
8
4a
4b
4c
4d
4e
4f
Ph
80
75
73
82
75
80
59
65
18.2, 25.0
18.6, 25.1
18.0, 25.1
18.3, 24.5
17.2, 25.3
14.5, 25.4
18.6, 24.7
19.2, 23.0
17.1, 24.8
16.5, 25.0
16.9, 25.5
17.2, 24.5
16.2, 25.1
14.5, 25.3
20.4, 23.8
18.9, 22.7
>95 : 5
>95 : 5
>95 : 5
>95 : 5
>95 : 5
91 : 9
1-Naphthyl
2-Naphthyl
p-MeO–C6H4
p-CF3–C6H4
2-Furyl
2,4,6-Me3C6H2
i-Pr
4g
4h
85 : 15
87 : 13
a Isolated yield. b Determined by 31P NMR.
of aldimines as well as its effects in stereoselective nucleophilic
addition reactions is well documented.16
was used as a base (Table 1, Entry 5) and, in the same solvent,
the hydrophosphinylation reaction did not proceed in the absence
of a base (Table 1, Entries 6–7). The conversions in THF at low
temperature were finally improved to almost quantitative when the
amount of ZnEt2/TMEDA was increased (Table 1, Entries 10–14)
without dropping in the diastereoselectivities.
With these results in hands we extended the hydrophosphony-
lation reaction to several aromatic diphenylphosphinyl aldimines
(Table 2). Treatment of N-diphenylphosphinyl aldimines in THF
at -80 ◦C with TADDOL phosphonate 3 in the presence of
1.2 eq. of ZnEt2 and TMEDA during 12 h afforded in good
yields the corresponding aminophosphonates 4 with very good
diastereoselectivities.
Moreover, although very good conversions were obtained in
general at low temperature when the reaction was performed
using one equivalent of LDA as a base (Table 1, Entries 1, 3,
8), much better diastereoselectivities with still a good yield are
obtained when ZnEt2 is used instead (Table 1, Entries 2, 4, 10).
The presence of one equivalent of tetramethylethylenediamine
(TMEDA) is crucial in order to favour the solubility of ZnEt2
in THF at low temperature by a coordination effect between
the Zn and N atoms, since very low yields were obtained when
TMEDA was not present (Table 1, Entry 9). Switching the solvent
to CH2Cl2 did not improve the diastereoselectivity when Et3N
4256 | Org. Biomol. Chem., 2010, 8, 4255–4258
This journal is
The Royal Society of Chemistry 2010
©

View Online
The reaction is applicable to N-diphenylphosphinyl aryl
aldimines (R = Ph, 1-naphthyl, 2-naphthyl), bearing electron rich
(R = p-MeO–C6H4, Table 2, Entry 4) and electron poor (R = p-
CF3–C6H4, Table 2, Entry 5) substituents as well as heteroaromatic
groups (R = 2-furyl, Table 2, Entry 6) at the a position. A
substantial drop in the yield and diastereoselectivity was observed
when an ortho substituted arylimine was used which may be due
to the steric crowding in the electrophilic imine carbon (R = 2,4,6-
Me3C6H2, Table 2, Entry 7). Previous reports have described the
generation ‘in situ’ of N-phosphinylimines from phosphorylated
aminosulfones using ZnEt2 as base.17 In our case, an important
fall in the diastereoselectivity and conversion was observed when
aromatic N-phosphinylimines were generated ‘in situ’ with ZnEt2
and subsequently treated with TADDOL phosphite 3 in the
presence of TMEDA (60% yield, d.r. = 65 : 45).
The diastereoselective addition of TADDOL phosphite 3 was
also extended to imines derived from aliphatic aldehydes. Al-
though required aliphatic imines are normally only available ‘in
situ’, isolation of N-phosphinylimine derived from isobutyralde-
hyde, from the corresponding aminosulfone, by b-elimination of
sulfonic acid using NaHCO3 as base, followed by filtration and
evaporation is feasible. Treatment of unpurified N-phosphinyl
isobutyraldimine in the optimized conditions afforded the target
aminophosphonate 4h in moderate yield and diastereoselectivity
(Table 2, Entry 8).
It should be emphasized that pure samples of the major
diastereoisomer can be obtained in all cases by simple purification
of the crude mixtures by chromatography. This strategy represents
an improvement not only in conversions but also in the diastereos-
electivities respect to the other two reported examples of addition
of chiral phosphites to imines.
The synthesis of enantiopure aminophosphonic acids 5 is
achieved by simultaneous hydrolysis of (R,R)-TADDOL phos-
phite and diphenylphosphinyl groups of the major diastereoisomer
of a-aryl and a-alkyl a-aminophosphonates 4a,h in refluxing
aqueous HCl 4 N (Scheme 2, 77–82%). The monitoring of selective
deprotection of amino group in milder conditions, at room
temperature and increasing the concentration of hydrochloric
acid from 0.1 M to 2 M, showed mixtures of mono-deprotected
phosphonate and double-deprotected phosphonic acid. Compar-
ison of the optical rotation with literature values showed an (R)
absolute configuration for the aminophosphonic analog of (R)-
phenylglycine 5a (R = Ph) and (R)-valine 5b (R = i-Pr).
Fig. 2 Model for the hydrophosphonylation of N-diphenylphosphinoyl
imines with (R,R)-TADDOL phosphite 3.
in the metalated phosphite tautomer is expected to adopt an axial
orientation due to the anomeric effect and the Zn counteranion
ionically bonded to the oxygen would be coordinated to the
lone pair of the iminic nitrogen. The diphenylphosphinoyl group
pointing opposite to the Zn makes the imine approach to the
phosphite lone pair with the appropriate orientation for the
nucleophilic attack of the phosphorus to the Re face.
Conclusions
In summary we report an easy synthesis of enantiopure a-
aminophosphonic acid derivatives through diastereoselective hy-
drophosphonylation of N-diphenylphosphinylimines using an
efficient (R,R)-TADDOL derived phosphorus nucleophile. Eas-
ily available (R,R)-TADDOL phosphite, prepared from very
cheap comercially available natural tartaric acid, affords (R)-a-
aminophosphonic acids. This is not trivial, since it is well known
that in most of the occasions (R) forms of a-aminophosphonic
acids2,6 are more active than their (S) isomers. As far as we know
the results reported here represent the best conversions and/or
diastereoselectivities reported so far in the addition of chiral
phosphites to imines.
Experimental section
Representative example for the diastereoselective
hydrophosphonylation of imines using TADDOL phosphite 3.
Synthesis of 1,3-dioxolo[4,5-e][1,3,2]dioxaphosphepin,
tetrahydro-2,2-dimethyl-6-[diphenylphosphinoylamino-1-
phenylmethyl]-4,4,8,8 tetraphenyl-, 6-oxide, (3aR,8aR) (4a)
TADDOL phosphite 3 (1.0 g, 1.95 mmol) was dissolved in dry
THF (15 mL) and the solution was cooled down to -80 ◦C. A
1.1 M solution of Et2Zn in toluene (2.14 mL) and TMEDA
(0.3 mL, 1.95 mmol) were injected and the mixture was stirred for
15 min at -80 ◦C. After that time the solution of N-benzylidene-
P,P-diphenylphosphinic amide (0.60 g, 1.95 mmol) in dry THF
(15 mL) was added dropwise. The stirring was continued for 12 h
at -80 ◦C before quenching with sat. aq. NH4Cl (15 mL). The
layers were separated and the aqueous layer was extracted with
CH2Cl2 (3 ¥ 30 mL). The combined organic extracts were dried
over anhydrous MgSO4 and concentrated under reduced pressure
affording crude product that was further purified by column
chromatography (SiO2, EtOAc/Hexane) affording 1.28 g (80%) of
4a as a white solid. Mp. 165–167 ◦C. [a]D20 -111.4 (c 1.0, CH2Cl2). Rf
(EtOAc/Pentane 2 : 1): 0.40. 1H NMR (300 MHz, CDCl3): d 0.43
(s, 3H, CH3), 0.88 (s, 3H, CH3), 3.75–3.80 (m, 1H, NH), 4.68–
Scheme 2 Simultaneous deprotection of amino and phosphonate groups.
According to the configuration of the stereogenic center we
propose a model for the addition of phosphite18 where the seven
membered ring adopts a more stable boat conformation fixed by
the trans configuration of the five-membered ring, where the two
heteroatoms adopt the most stable equatorial orientation with the
two hydrogens in axial conformation (see Fig. 2). The alkoxy group
3
4.83 (m, 1H, CHP), 4.96 (d, JHH = 8.0 Hz, 1H, CHO), 5.54 (d,
This journal is
The Royal Society of Chemistry 2010
Org. Biomol. Chem., 2010, 8, 4255–4258 | 4257
©

View Online
3JHH = 8.0 Hz, 1H, CHO), 6.96–7.90 (m, 35H, CHar).13C NMR
6 (a) P. Merino, E. Marques-Lopez and R. P. Herrera, Adv. Synth.
Catal., 2008, 350, 1195–1208; (b) T. Vilaivan, W. Bhanthumnavin and
Y. Sritana-Anant, Curr. Org. Chem., 2005, 9, 1315–1392; (c) H. Gro¨ger
and B. Hammer, Chem.–Eur. J., 2000, 6, 943–948.
7 (a) Recent contributions: F. Shi and B. Song, Org. Biomol. Chem.,
2009, 7, 1292–1298; (b) S. Nakamura, H. Nakashima, A. Yamamura,
N. Shibata and T. Toru, Adv. Synth. Catal., 2008, 350, 1209–1212;
(c) J. P. Abell and H. Yamamoto, J. Am. Chem. Soc., 2008, 130, 10521–
10523; (d) G. D. Joly and E. N. Jacobsen, J. Am. Chem. Soc., 2004, 126,
4102–4103.
8 O. I. Kolodiazhnyi, E. V. Grishkun, S. Sheiko, O. Demchuk, H.
Thoennessen, P. G. Jones and R. Schmutzler, Tetrahedron: Asymmetry,
1998, 9, 1645–1649.
9 (a) For a recent review see: F. Palacios, C. Alonso and J. M. de los
Santos, Chem. Rev., 2005, 105, 899–931; (b) F. Palacios, A. M. Ochoa
de Retana, J. Oyarzabal, S. Pascual and G. Fernandez de Troconiz,
J. Org. Chem., 2008, 73, 4568–4574.
10 (a) J. Vicario, Do. Aparicio and F. Palacios, J. Org. Chem., 2009, 74,
452–455; (b) J. M. De los Santos, R. Ignacio, D. Aparicio and F.
Palacios, J. Org. Chem., 2007, 72, 5202–5206; (c) F. Palacios, J. Vicario,
A. Maliszewska and D. Aparicio, J. Org. Chem., 2007, 72, 2682–2685;
(d) F. Palacios, A. M. Ochoa de Retana and J. M. Alonso, J. Org. Chem.,
2005, 70, 8895–8901; (e) F. Palacios, D. Aparicio, Y. Lo´pez and J. M. de
los Santos, Tetrahedron Lett., 2004, 45, 4345–4348; (f) F. Palacios, D.
Aparicio, A. M. Ochoa de Retana, J. M. de los Santos, J. I. Gil and R.
Lopez de Munain, Tetrahedron: Asymmetry, 2003, 14, 689–700; (g) F.
Palacios, D. Aparicio, A. M. Ochoa de Retana, J. M. de los Santos, J. I.
Gil and J. M. Alonso, J. Org. Chem., 2002, 67, 7283–7288.
1
(75 MHz, CDCl3): d 26.4 (CH3), 27.2 (CH3), 53.4 (d, JPC
=
=
=
3
3
161.7 Hz, CHP), 79.1 (d, JPC = 2.0 Hz, CHO), 80.2 (d, JPC
2
2
2.0 Hz, CHO), 87.1 (d, JPC = 8.4 Hz, CPh2), 91.0 (d, JPC
13.4 Hz, CPh2), 113.8 (C(CH3)2), 126.6 (2 ¥ CHar), 127.2 (2 ¥
CHar), 127.3 (2 ¥ CHar), 127.4 (2 ¥ CHar), 127.6 (CHar), 127.8
3
(CHar), 127.9 (CHar), 128.0 (2 ¥ CHar), 128.1 (d, JPC = 5.4 Hz,
2 ¥ CHar), 128.3 (2 ¥ CHar), 128.4 (4 ¥ CHar), 128.5 (CHar), 128.6
3
(d, JPC = 7.8 Hz, 2 ¥ CHar), 128.9 (2 ¥ CHar), 129.8 (2 ¥ CHar),
1
131.2 (d, JPC = 102.3 Hz, 2 ¥ Cq), 131.9 (CHar), 132.0 (CHar),
132.1 (2 ¥ CHar), 132.2 (CHar), 132.3 (2 ¥ CHar), 132.6 (d, 3JPC
=
9.1 Hz, 2 ¥ CHar), 136.4 (Cq), 139.4 (Cq), 139.6 (Cq), 143.7 (Cq),
144.3 (d, 2JPC = 7.6 Hz, Cq). 31P NMR (120 MHz, CDCl3): d 18.2
3
3
(d, JPP = 39.7 Hz, PO(OR)2), 25.2 (d, JPP = 39.7 Hz, POPh2).
FTIR (neat) nmax/cm-1: 3432 (N–H st), 1225 (P O st). CIMS m/z
(amu): 818 ([M+H], 100). HRMS (amu) Calcd for C50H46NO6P2
(M+H)+ 818.2800; Found, 818.2772.
Acknowledgements
The present work has been supported by the Direccio´n General de
Investigacio´n del Ministerio de Ciencia e Innovacio´n (MICINN,
Madrid DGI, CTQ2009-12156) and by the Departamento de
Educacio´n, Universidades e Investigacio´n del Gobierno Vasco
and Universidad del Pa´ıs Vasco (GV, IT 422-10; UPV, GIU-
09/57). J. V. thanks the Ministerio de Ciencia e Innovacio´n
for a “Ramo´n y Cajal contract”. T.K.O. acknowledges the
contract from Universidad del Pa´ıs Vasco, programme Ayudas de
Especializacio´n para Investigadores Doctores 2008. UPV/EHU-
SGIker technical support (MICINN, GV/EJ, European Social
Fund) is gratefully acknowledged.
11 (a) J. Vicario and F. Palacios, Org. Lett., 2006, 8, 5405–5408; (b) J.
Vicario and F. Palacios, Synthesis, 2007, 3923–3925.
12 During our preliminary analysis of several chiral phosphorus nucle-
ophiles we found that cleavage of endocyclic P–O bonds in BINOL
phosphite (III) is very easy due to the twisted structure of BINOL
auxiliary and the low stability of the 7-membered ring including four sp2
carbons. For instance, trans esterification is fast if BINOL phosphites
are dissolved in alcoholic solvents. That might be the reason of the
low yields achieved in the addition of BINOL phosphite (III) towards
BF3-activated 3-thiazolines. (See ref. 17).
13 I. Schlemminger, A. Lu¨tzen, A. Willecke, W. Maison, R. Koch, W. Saak
and J. Martens, Tetrahedron Lett., 2000, 41, 7285–7288.
14 (a) For recent contributions with TADDOL phosphite IV see: M. R.
Garret, J. C. Tarr and J. S. Johnson, J. Am. Chem. Soc., 2007, 129,
12944–12945; (b) D. Enders, L. Tedeschi and D. Fo¨rster, Synthesis,
2006, 1447–1469; (c) L. Ackermann, C. J. Gschrei, A. Althammer and
M. Riederer, Chem. Commun., 2006, 1419–1421; (d) M. R. Nahm, J. R.
Potnick, P. S. White and J. S. Johnson, J. Am. Chem. Soc., 2006, 128,
2751–2756.
Notes and references
1 For an excellent book see: V. P. Kukhar, H. R. Hudson, ed. in
Aminophosphonic and Aminophopshinic Acids. Chemistry and Biological
Activity. J Wiley, Chichester, 2000.
15 F. Toda and K. Tanaka, Tetrahedron Lett., 1988, 29, 551–554.
16 (a) Some selected examples of diastereoselective nucleophilic additions
to diphenylphosphinyl aldimines: R. B. Lettan II, C. C. Woodward and
K. A. Scheidt, Angew. Chem., Int. Ed., 2008, 47, 2294–2297; (b) H.
Morimoto, S. H. Wiedemann, A. Yamaguchi, S. Harada, Z. Chen,
S. Matsunaga and M. Shibasaki, Angew. Chem., Int. Ed., 2006, 45,
3146–3150; (c) M. Sugita, A. Yamaguchi, N. Yamagiwa, S. Handa, S.
Matsunaga and M. Shibasaki, Org. Lett., 2005, 7, 5339–5342; (d) T.
Yoshida, H. Morimoto, N. Kumagai, S. Matsunaga and M. Shibasaki,
Angew. Chem., Int. Ed., 2005, 44, 3470–3474; (e) G. Grach, J. Sopkova-
de Oliveira Santos, J. Lohier, L. Mojovic, N. Ple´, A. Turck, V. Reboul
and P. Metzner, J. Org. Chem., 2006, 71, 9572–9579; (f) S. Matsunaga,
T. Yoshida, H. Morimoto, N. Kumagai and M. Shibasaki, J. Am. Chem.
Soc., 2004, 126, 8777–8785.
2 (a) For reviews see: P. Kafarski and B Lejczak, Curr. Med. Chem.: Anti-
Cancer Agents, 2001, 1, 301–312; (b) J. Grembecka and P. Kafarski,
Mini-Rev. Med. Chem., 2001, 1, 133–144; (c) P. Kafarski and B. Lejczak,
Phosphorus, Sulfur Silicon Relat. Elem., 1991, 63, 193–215.
3 (a) R. Hirschmann, A. B. Smith III, C. M. Taylor, P. A. Benkovic, S. D.
Taylor, K. M. Yager, P. A. Sprengeler and S. J. Venkovic, Science, 1994,
265, 234–237; (b) B. Lejczak, P. Kafarski, H. Sztajer and P. Mastarlerz,
J. Med. Chem., 1986, 29, 2212–2217; (c) J. Oleksyszyn and J. C. Powers,
Biochemistry, 1991, 30, 485–493; (d) P. A. Bartlett, J. E. Hanson and
P. G. Giannousis, J. Org. Chem., 1990, 55, 6268–6274; (e) M. C. Allen,
W. Fuhrer, B. Tuck, R. Wade and J. M. Wood, J. Med. Chem., 1989,
32, 1652–1661; (f) F. R. Atherton, C. H. Hassall and R. W. Lambert,
J. Med. Chem., 1986, 29, 29–40.
4 (a) W. W. Smith and P. A. Bartlett, J. Am. Chem. Soc., 1998, 120, 4622–
4628; (b) D. Bonarska, H. Kleszczyn´ska and J. Sarapuk, Cell Mol. Biol.
Lett., 2002, 7, 929–935.
5 (a) V. A. Alfonsov, Phosphorus, Sulfur Silicon Relat. Elem., 2008, 183,
2637–2644; (b) A. N. Pudovik, Dokl. Akad. Nauk SSSR, 1952, 83,
865–868.
17 (a) A. Cote´, A. A. Boezio and A. B. Charette, Proc. Natl. Acad. Sci.
U. S. A., 2004, 101, 5405–5410; (b) J.-N. Desrosiers, A. Cote´ and A. B.
Charette, Tetrahedron, 2005, 61, 6186–6192.
18 J. L. Pirat, J. Monbrun, D. Virieux, J.-N. Volle, M. Tillard and H. J.
Cristau, J. Org. Chem., 2005, 70, 7035–7041.
4258 | Org. Biomol. Chem., 2010, 8, 4255–4258
This journal is
The Royal Society of Chemistry 2010
©