New strategy for the synthesis of phosphatase inhibitors TMC-69-6H and analogs

Article abstract of DOI:10.1016/j.tetlet.2006.10.102

An efficient method for the synthesis of antitumor TMC-69-6H and related analogs which have been demonstrated to be phosphatase (PTP1B, VHR, and PP1) inhibitors, is reported. This strategy involves two key steps: a diastereoselective aldol reaction and a

Full text of DOI:10.1016/j.tetlet.2006.10.102

Tetrahedron Letters 47 (2006) 9305–9308
New strategy for the synthesis of phosphatase inhibitors
TMC-69-6H and analogs
Nicolas Brondel, Brigitte Renoux* and Jean-Pierre Gesson
`
´ ´
Laboratoire ‘Synthese et Reactivite des Substances Naturelles’, UMR CNRS 6514 40, Avenue du Recteur Pineau,
F-86022 Poitiers Cedex, France
Received 6 September 2006; revised 19 October 2006; accepted 20 October 2006
Abstract—An efficient method for the synthesis of antitumor TMC-69-6H and related analogs which have been demonstrated to be
phosphatase (PTP1B, VHR, and PP1) inhibitors, is reported. This strategy involves two key steps: a diastereoselective aldol reaction
and a one-pot tandem ring-closing and cross metathesis for the construction of the pyran moiety.
Ó 2006 Elsevier Ltd. All rights reserved.
Isolated from the fermentation broth of a mitosporic
fungus, Chrysosporium sp. TC 1068, labile TMC-69 (1)
was described as a new antitumoral antibiotic.1 Its hexa-
hydro derivative TMC-69-6H (2), with improved stabil-
ity, was prepared by Khono. These two compounds
TMC-69 (1) and TMC-69-6H (2) showed cytotoxic
activities in vitro against various tumor cell lines (IC50
values of 0.1–1.87 lM). Compound 2 induced significant
prolongation of survival time of mice transplanted with
B16 melanoma as well as P388 leukemia (ILS value of
58.1% at a dose of 3 mg/kg). Moreover, TMC 69-6H
(2) was found to have inhibitor activity against Cdc25A
and B phosphatases (dose dependent inhibition of
Cdc24A activity with an IC50 of 3.1 lM).2 Cdc25 phos-
phatases are classified as dual-specificity protein phos-
phatases that act as keys regulators of the cell cycle
progression and mitogenic signaling pathways. These
phosphatases which are overexpressed in many human
tumors constitute potential targets for drug discovery.
phatase PTP1B, the dual specific phosphatase VHR,
and the serine/threonine phosphatase PP1. PTP1B is a
key regulator of insulin–receptor activity5 and is ex-
pected to enhance insulin sensitivity and act as effective
therapeutics for the treatment of Type II diabetes, insu-
lin resistance, and obesity. Phosphatase PP1 plays an
important role in the regulation of the cell cycle.6
In spite of a completely different selectivity profile, these
compounds constitute a promising new class of selective
phosphatase inhibitors (see Scheme 1).
OH
O
N
O
OH
TMC-69
The first total synthesis of TMC-69-6H and analogs was
1
described by Furstner et al.3 All these compounds were
¨
evaluated for their biological activity,4 but the previ-
ously reported strong inhibition of Cdc25A and B phos-
phatases was not confirmed. It should be noted that
antitumor activity of TMC-69-6H remains undisputed.
OH
O
Furstner found that TMC-69-6H and congeners exhibit
¨
pronounced activities against the tyrosine protein phos-
N
O
OH
TMC-69-6H
Keywords: TMC-69-6H; Antitumor activity; PTP1B inhibitor; Diaste-
reoselective aldolization; Metathesis.
2
*
Scheme 1. TMC-69 and TMC-69-6H.
Corresponding author. E-mail: brigitte.renoux@univ-poitiers.fr
0040-4039/$ - see front matter Ó 2006 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tetlet.2006.10.102

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N. Brondel et al. / Tetrahedron Letters 47 (2006) 9305–9308
TMC-69-6H
OP
OP
N
O
O
Cl
N
OP
Cl
OP
OP OH
OH
Cl
Scheme 2. Retrosynthetic analysis.
N
OP
Cl
N
H
O
We now report a new flexible strategy for the diastereo-
selective synthesis of TMC-69-6H and derivatives from
pyridone moiety via two key steps, diastereoselective
aldolization followed by tandem ring-closing and cross
metathesis for the construction of pyran moiety. The
key aspects of the retrosynthetic analysis applied in this
study are outlined in Scheme 2.
produced the known 6-pyridone 5 in 56% yield (Scheme
3).
Pyridone 5 was submitted to the formylation conditions.
The Reimer–Thiemann reaction8 has been successfully
extended to pyridone derivatives (Scheme 3). Electro-
philic addition of dichlorocarbene species generated by
the action of a base (NaOH) in chloroform in a two-
phase system, afforded the desired product 6 in 57%
yield.
We began our investigation by construction of the pyri-
done moiety using Davis conditions.7 Thus, condensa-
tion between phenylacetonitrile and maloyldichloride
The alkylation of ambient anions of pyridone has been
extensively studied.9 Whatever the conditions, a separa-
ble mixture of di-O-benzylated compound 7 and O- and
N-benzylated derivative 8 was isolated (Scheme 3). The
preferred di-O-alkylation was observed under typical
basic conditions (BnBr, K2CO3, DMF) to afford 7 in
54% yield.
O
Cl
+
Cl
O
3
N
4
Starting from 7, we investigated a new class of crotyl-
boron reagents and their Lewis acid-promoted additions
to carbonyl compounds as described by Thadani and
Batey.10 In a biphasic medium (CH2Cl2, H2O) contain-
ing a phase transfer catalyst (nBu4NI), the use of potas-
sium (E)-crotyltrifluoroborate 9 led to the formation of
anti-homocrotyl alcohols (dr > 95%) in 96% yield
(Scheme 4).
4 days
56%
OH
OH
CHO
O
CHCl3
NaOH aq. 30%
57%
Cl
N
H
O
Cl
N
H
6
5
The (E)-crotyltrifluoroborate gave the expected anti
product. This observation is consistent with the interme-
diacy of crotylboron difluoride, formed in situ by Lewis
acid-promoted removal of fluoride from 9, and addition
via a Zimmerman–Traxler like transition state.11
BnBr, K2CO3
DMF
54%
OBn
O
O
O
OBn
N
As shown in Scheme 5, propargylic ether 11 was pre-
pared according to the procedure in the literature.12
Treatment of compound 10 with NaH and propargyl
bromide gave enyne 11 in 90% yield.
H
H
+
Cl
N
OBn
Cl
Bn
7
8
Metal-catalyzed enyne metathesis seemed to be a
convenient approach to achieve the synthesis of the
Scheme 3. Pyridone synthesis.

N. Brondel et al. / Tetrahedron Letters 47 (2006) 9305–9308
9307
K+
If highly oxygenated functionality enynes did not inhibit
catalytic activity, it should be noted that ethylene atmo-
sphere is required to facilitate metathesis of enyne as
mentioned previously15 (see Scheme 6).
BuLi
-
tBuOK
B(OiPr)3
At this stage, introduction of lateral side chain has been
considered via cross metathesis reaction. Alkene 13 was
prepared by alkylation of butan-2-one with a suitable
Grignard reagent. The resulting alcohol was submitted
to acidic conditions (APTS, benzene, 80 °C) to yield
13 as an inseparable mixture of 6-methyl-octa-1,6-diene
and 6-methyl-octa-1,5-diene.
K+
F
MeOH
F
B
O
O
B
F
KHF2 / H2O
9
Under known conditions (Grubbs I 5 mol %, excess of
13, CH2Cl2), the single cross metathesis adduct 14 was
isolated in 76% yield.
OBn
O
OBn OH
+
9
I
NBu4
H
CH2Cl2/H2O
96%
In view of these two successive metathesis, a tandem or
domino reaction which could shorten the synthetic route
to TMC-69-6H analogs was studied. The enyne meta-
thesis was first carried out as previously described for
12 h. Then, ethylene gas was removed and the reaction
mixture was concentrated to the desired cross metathesis
dilution.16 Addition of alkene 13 afforded compound 14
in 69% overall yield.
Cl
N
OBn
Cl
N
OBn
10
( )
7
Scheme 4. Batey’s crotylation conditions.
OBn OH
NaH
OBn
N
O
THF
Reduction of double bonds and hydrogenolysis of both
chloride and benzyl groups by catalytic hydrogenation
furnished a separable mixture of the desired product
(R) ( )-15 and its C10 epimer (S) ( )-15 in, respectively,
28% and 11% isolated yield. Whatever the conditions of
reduction (solvent, temperature, reaction time), the
partially reduced product ( )-16 was recovered in 29%
yield (see Scheme 7).
90%
Cl
N
OBn
Cl
OBn
Br
( ) 10
( ) 11
Scheme 5. Propargyl ether.
trisubstituted oxygen heterocycle.13 In a first attempt,
compound 11 was treated with ruthenium catalyst in
dichloromethane at room temperature under ethylene
gas. The first generation Grubbs‘s catalyst effected
enyne metathesis of the substrate tethered with terminal
alkyne, affording the pyranyl diene 12 in good yield
(82%).14
The compound (R) ( )-15 matches the literature data
reported for TMC-69-6H very well.17 The axial orienta-
tion of the alkyl chain on the tetrahydropyran ring in
(R) ( )-15 was evident from an analysis of the pertinent
constants data (Fig. 1). The C-10 epimer is characterized
in 1H NMR by a similar 3J between H-7 and H-8
OBn
O
OBn
O
Grubbs I
5 mol%
CH2CH2
82%
Cl
N
OBn
Cl
N
OBn
( ) 12
( ) 11
Grubbs I
5 mol%
CH2Cl2
+
one pot
Grubbs I, CH2CH2, 12hrs
76%
13a,b
69%
then, 13a,b
OBn
O
Cl
N
OBn
( )-14
Scheme 6. Tandem ring-closing and cross metathesis.

9308
N. Brondel et al. / Tetrahedron Letters 47 (2006) 9305–9308
pyridone moiety and the lateral side chain. Further-
more, enantioselective synthesis is under study and will
be reported in due course.
OBn
O
Cl
N
OBn
Acknowledgments
( )-14
H2, Pd/C
We thank MENRT and CNRS for financial support.
References and notes
OH
1. Hirano, N.; Khono, J.; Tsunoda, S.; Nishio, M.; Kishi, N.;
Okuda, T.; Kawano, K.; Komatsubara, S.; Nakanishi, N.
J. Antibiot. 2001, 54, 421–427.
2. Kohno, J.; Hirano, N.; Sugawara, K.; Nishio, M.;
Hashiyama, T.; Nakanishi, N.; Komatsubara, S. Tetra-
hedron 2001, 57, 1731–1735.
O
(10
R)( )-15
N
H
O
28%
+
3. Furstner, A.; Feyen, F.; Prinz, H.; Waldmann, H. Angew.
¨
OH
Chem., Int. Ed. 2003, 42, 5361–5364.
4. Furstner, A.; Feyen, F.; Prinz, H.; Waldmann, H. Tetra-
¨
O
hedron 2004, 60, 9543–9558.
5. Elchebly, M.; Payette, P.; Michaliszyn, E.; Cromlish, W.;
Collins, S.; Loy, A. L.; Normandin, D.; Cheng, A.;
Himms-Hagen, J.; Chan, C. C.; Ramachandran, C.;
Gresser, M.; Tremblay, M. L.; Kennedy, B. P. Science
1999, 283, 1544–1548; Moller, N. P.; Iversen, L. F.;
Andersen, H. S.; McCormack, J. G. Curr. Opin. Drug
Discovery 2000, 3, 527–540.
(10S)( )-15
N
H
O
11%
+
OH
6. Shenolicar, S. Annu. Rev. Cell Biol. 1994, 10, 55–86.
7. Davis, S. J.; Elvidge, J. A.; Foster, A. B. J. Chem. Soc.
1962, 3638–3644.
8. Mohamed E. A.; Abdel-Rahman R. M.; Tawfik A. M.;
Ismail M. M. CAN 121:83299 AN 1994:483299 CAPLUS.
9. Sato, T.; Yoshimatsu, K.; Otera, J. Synlett 1995, 845–846;
McGee, K. F.; Al-Tel, T. H.; Sieburth, S. McN. Synthesis
2001, 8, 1185–1196; Comins, D. L.; Jianhua, G. Tetra-
hedron Lett. 1994, 35, 2819–2822.
O
( )-16
29%
N
H
O
Scheme 7. Analogs of TMC-69-6H.
10. Thadani, A. N.; Batey, R. A. Org. Lett. 2002, 4, 3827–
3830.
11. (a) Batey, R. A.; Thadani, A. N.; Smil, D. V. Tetrahedron
Lett. 1999, 40, 4289–4292; (b) Roush, W. R.; Adam, M.
A.; Walts, A. E.; Harris, D. J. J. Am. Chem. Soc. 1986,
108, 3422–3434.
H
8
9 H
10
Me
H
R
H
7
11
H
H
H
12. Kim, J. N.; Ryu, E. K. Synth. Commun. 1996, 26, 67–74.
13. (a) Kinoshita, A.; Mori, M. Synlett 1994, 1020–1022; (b)
Sanford, M. S.; Love, J. A.; Grubbs, R. H. J. Am. Chem.
Soc. 2001, 123, 6543–6554; (c) Cavallo, L. J. Am. Chem.
Soc. 2002, 124, 8965–8973.
Figure 1. Schematic representation of compound (R) ( )-15 with
characteristic NOESY data. The following coupling constants indicate
a chair conformation of the tetrahydropyran ring and an axial
orientation for the alkyl side chain: 3JH-7,H-8 = 10.5 Hz, 3JH-10,H-11ax
=
3
2.1 Hz, and JH-10,H-11eq = 1 Hz.
14. Guo, H.; Madhushaw, R.; Shen, F. M.; Liu, R. S.
Tetrahedron 2002, 58, 5627–5637.
15. Diver, S. T.; Giessert, A. J. Chem. Rev. 2004, 104, 1317–
1382.
(3JH-7,H-8 = 10.5 Hz) as for (R) ( )-15 and by a change
in the 3J between H-10 and H-11 (3JH-10,H-11ax
=
16. Blackwell, H. E.; O’Leary, D. J.; Chatterjee, A. K.;
Washenfelder, R. A.; Bussmann, D. A.; Grubbs, R. H. J.
Am. Chem. Soc. 2000, 122, 58–71.
3
11.4 Hz and JH-10,H-11eq = 2.3 Hz). This observation is
in agreement with a quasi-equatorial position of the side
chain.
1
17. (R) ( )-15 NMR: H NMR (CDCl3, 300 MHz, d) 0.85–
0.90 (m, 9H), 1.24–1.60 (m, 15H), 1.76 (d, 1H,
J = 12.8 Hz), 2.02 (m, 1H), 3.72 (dd, 1H, J = 2.1 and
11.6 Hz), 3.94 (d, 1H, J = 11.5 Hz), 4.63 (d, 1H,
J = 10.5 Hz), 7.32–7.48 (m, 6H), 9.60 (sl, 1H). TMC 69-
6H lit.2: 0.83–0.85 (m, 9H), 1.11–1.63 (m, 15H), 1.77 (1H,
br d), 2.08 (m, 1H), 3.72 (dd, 1H, 11.6, 2.5), 3.96 (br d,
11.6), 4.68 (d, 10.5, 1H), 7.35 (m, 1H), 7.41 (m, 2H), 7.46
(m, 2H), 9.51 (br s, 1H).
In summary, we have developed a short and flexible
strategy to prepare TMC-69-6H and analogs. The
reported chemistry will provide a diverse collection of
compounds of particular interest for generating struc-
ture–activity relationships (SAR). Some structural mod-
ifications are in progress in our laboratory including the