Cystine mimetics - Solid phase lanthionine synthesis

Article abstract of DOI:10.1016/j.tetlet.2003.12.074

The total solid phase synthesis of an analogue of the B ring of nisin was achieved, in a biomimetic fashion, via the solid phase diastereoselective cyclisation of a dehydrothiol-containing peptide.

Full text of DOI:10.1016/j.tetlet.2003.12.074

Tetrahedron
Letters
Tetrahedron Letters45 (2004) 1399–1401
Cystine mimetics––solid phase lanthionine synthesis
Mizio Matteucci,a Gurdip Bhalayb and Mark Bradleya,*
aCombinatorial Centre of Excellence, Department of Chemistry, University of Southampton, Southampton S017 1BJ, UK
bNovartis Pharma, Wimblehurst Road, Horsham RH12 5AB, UK
Received 17 October 2003; revised 4 December 2003; accepted 11 December 2003
Abstract—The total solid phase synthesis of an analogue of the B ring of nisin was achieved, in a biomimetic fashion, via the solid
phase diastereoselective cyclisation of a dehydrothiol-containing peptide.
Ó 2003 Elsevier Ltd. All rights reserved.
Lanthioninesare a group of unnatural amino acids
found in a range of natural products, most notably in
the lantibiotics,1 a class of polycyclic peptide antibac-
terials possessing a broad range of biological activities.
Lanthionine isalos a motif, which hasbeen widely
i
Boc-Phe-Cys(Me)-Cys(Trt)-OMe
Boc-Phe-Cys((O)Me)-Cys(Trt)-OMe
ii
iii
Boc-Phe-Dha-Cys-OMe
Boc-Phe-Dha-Cys(Trt)-OMe
2
1
2
adopted asa peptidomimetic of cystine.
Scheme 1. Reagentsand conditions: (i) H 2O2 (60% solution in H2O,
5 equiv)/Sc(OTf)3 (0.2 equiv) in CH2Cl2/10% EtOH, 15 min, 96%; (ii)
DBU (2 equiv) in CH3OH, 1 h, 44%; (iii) 1% TFA, TIS (3 equiv) in
CH2Cl2, 55%. Trt ¼ triphenylmethyl; Sc(OTf)3 ¼ scandium trifluoro-
methane sulfonate; DBU ¼ 1,8-diazabicyclo[5.4.0]undec-7-ene; Dha ¼
dehydroalanine; TFA ¼ trifluoroacetic acid; TIS ¼ triisopropylsilane.
Several approacheshave been explored to acceslan-
thionines in solution phase methods3–7 and have in-
cluded
a
total synthesis of nisin,8 while several
biomimetic solution phase syntheses via the Michael
addition of a cysteine residue onto a dehydroalanine-
containing peptide have been reported.6
group, all in reasonable yield. The ability to use excess
oxidant and a solvent system rich in dichloromethane,
rendered this approach highly suitable for solid phase
applications.
On the solid phase, there are few examples of cyclic
lanthionine synthesis.2d;9 One of the most recent
advancesin thisfield focused on the preparation of an
analogue of the B ring of nisin but, for synthetic reasons,
the precursor dehydrothiol was assembled via a segment
condensation approach.6e
The high chemoselectivity of this method enabled the
generation of a resin bound dehydrothiol peptide using
methyl cysteine as a ÔmaskedÕ dehydroalanine moiety.
This peptide, following further synthetic elaborations,
was cyclised to give the desired lanthionyl derivative
both in solution and on the solid phase.
Recently, a mild and highly selective oxidation proce-
10
dure wasdecsribed by Matteucci
that enabled the
synthesis of S-methylcysteine sulfoxides in the presence
of a variety of acid labile protecting groups, including S-
trityl protected cysteine residues. This method was
exploited here to prepare the dehydrothiol tripeptide 211
(Scheme 1) by selective oxidation, base mediated elimi-
nation and acidic removal of the cysteine protecting
To achieve these goals, peptide 3 was assembled on PS
resin equipped with a Rink linker. This was exposed to
the oxidizing conditions(H O2/cat. Sc(OTf)3) and trea-
2
ted with 5% DBU for 5 h (Scheme 2) to give, following
acidic cleavage, peptide 5 in good purity (76% by RP-
HPLC, UV detecton) proving the efficiency of the oxi-
dation/elimination sequence and achieving, for the first
time, the solid phase synthesis of a dehydrothiol without
Keywords: Solid phase synthesis; Lanthionine; Dehydro peptides;
Lantibiotics.
* Corresponding author. Tel.: +44-23-80593598; fax: +44-23-80596-
766; e-mail: mb14@soton.ac.uk
12
the need to prepare fragmentsin solution.
0040-4039/$ - see front matter Ó 2003 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tetlet.2003.12.074

1400
M. Matteucci et al. / Tetrahedron Letters 45 (2004) 1399–1401
S
STrt
H
O
O
O
O
H
N
H
N
RINK
RINK
Boc-N
H
N
N
N
N
H
N
H
N
H
O
O
O
O
O
3
i
O
O
S
STrt
H
O
H
N
H
N
Boc-N
H
N
N
H
N
H
N
H
O
O
O
4
ii, v
ii, iii
Figure 1. RP-HPLC traces(C column, UV detector, k ¼ 220 nm)
8
SR2
of (A) crude dehydrothiol peptide 5; (B) solution phase cyclisation;
(C) solid phase cyclisation.
O
O
O
H
H
N
H
R3-N
N
N
N R1
N
H
N
N
H
H
H
O
O
O
O
R1
=
RINK
R1 = R2 = R3 = H
7
5
The methods described above enable the efficient syn-
theissof peptidescontaining free thiolsand dehydro-
amino acidsuinsg the two orthogonally protected,
commercially available cysteine residues (S-Me and
S-Trt), which were easily incorporated using Fmoc
chemistry. The dehydrothiol peptide 5 could be cleaved
into solution for analysis and cyclisation or cyclised
directly on the solid phase to yield, stereoselectively, the
cyclic lanthionyl derivative 6, an analogue of the B ring
of nisin. This approach proves a general method for
lanthionyl synthesis (a stable mimetic of cystine) and is
amenable to peptidescontaining multiple S-Me and
S-Trt cysteine residues.
R2 = H, R3 = Boc
vi
iv
O
S
O
O
H
N
H
N
H
R3-N
H
N
N R1
N
H
N
H
N
H
O
O
O
O
R1
=
RINK
R3 = Boc
iii
R1 = R3 = H
8
6
Scheme 2. Reagentsand conditions: (i) H 2O2 (60% solution in H2O,
5 equiv)/Sc(OTf)3 (0.2 equiv) in CH2Cl2/10% EtOH, 20 min; (ii) 5%
DBU in CH2Cl2/CH3OH (1/1), 5 h; (iii) TFA/TIS/CH2Cl2 (95/2/3), 2 h;
(iv) H2O (pH ¼ 8.3), 20 min, 65%; (v) TFA/TIS/CH2Cl2 (2/2/96), 2 h;
(vi) 10% DBU in DMF, 15 h.
Before attempting the synthesis of cyclic lanthionine 6
on the solid phase, cyclisation was first carried out in
solution. Dehydrothiol peptide 5 was dissolved in water
(pH ¼ 8.3) and cyclisation was observed to occur rapidly
and cleanly (monitored by RP-HPLC, C8 column) to
give the expected meso-lanthionine 6 in 65% yield (after
RP-HPLC purification)12 as a single diastereoisomer, as
observed previously.2a;6b;e–g;9b
Acknowledgements
We thank Novartisand EPSRC for funding. The CCE is
supported through the JIF initiative (EPSRC).
References and notes
Cyclisation was then attempted on the solid phase
(Scheme 2). Thiol 7 wasgenerated by treating the
S-trityl protected precursor resin with a mildly acidic
cocktail (TFA/ TIS/CH2Cl2, 2/2/96). Several bases
(NMM, DIPEA, TEA) were used in order to promote
cyclisation. Surprisingly, very limited conversion to the
expected lanthionine were observed under these condi-
tions. This was believed to be due to residual acid
remaining in the resin and therefore the resins were
thoroughly washed with various solvents and solutions
of the bases in DMF prior to the basic treatment.
However, even this did not improve conversions. When
DBU was used as the base, the reaction was complete
within 15 h, showing for the first time that elimination
and cyclisation could be achieved on the solid phase.
1. (a) Jung, G. Angew. Chem., Int. Ed. Engl. 1991, 30, 1051–
1068; (b) Jack, R. W.; Sahl, H.-G. Trends Biotechnol. 1995,
13, 269–278; (c) Guder, A.; Wiedemann, I.; Sahl, H.-G.
Biopolymers (Peptide Science) 2000, 55, 62–73; (d) Jack,
R. W.; Jung, G. Curr. Opin. Chem. Biol. 2000, 4, 310–317.
€
2. (a) Polinsky, A.; Cooney, M. G.; Toy-Palmer, A.; Osapay,
G.; Goodman, M. J. Med. Chem. 1992, 35, 4185–4194; (b)
Goodman, M.; Shao, H. Pure Appl. Chem. 1996, 68, 1303–
1308; (c) Goodman, M.; Zapf, C.; Rew, Y. Biopolymers
(Peptide Science) 2001, 60, 229–245; (d) Rew, Y.; Malk-
mus, S.; Svensson, C.; Yaksh, T. L.; Chung, N. N.;
Schiller, P. W.; Cassel, J. A.; DeHaven, R. N.; Goodman,
M. J. Med. Chem. 2002, 45, 3746–3754.
3. (a) Desulfurisation of cystines: Harpp, D. N.; Gleason, J.
G. J. Org. Chem. 1971, 36, 73–80; (b) Cavelier-Frontin, F.;
Daunis, J.; Jacquier, R. Tetrahedron: Asymmetry 1992, 3,
85–94; (c) Galande, A. K.; Spatola, A. F. Lett. Pept. Sci.
2002, 8, 247–251.
Following acidic cleavage, the lanthionyl derivative was
purified by semi-preparative RP-HPLC and obtained as
a single diastereoisomer in 33% isolated overall yield
(from the starting aminomethyl resin). Data obtained
for the solution and solid phase cyclisation products
were identical (Fig. 1).13
ꢀ
4. (a) Thioalkylation of b-iodoalanines: Dugave, C.; Menez,
A. Tetrahedron: Asymmetry 1997, 8, 1453–1465; (b) Swali,
V.; Matteucci, M.; Elliott, R.; Bradley, M. Tetrahedron
2002, 58, 9101–9109; (c) Mohd Mustapa, M. F.; Harris,
R.; Bulic-Subanovic, N.; Elliott, S. L.; Bregant, S.;

M. Matteucci et al. / Tetrahedron Letters 45 (2004) 1399–1401
1401
Groussier, M. F. A.; Mould, J.; Schultz, D.; Chubb, N. A.
L.; Gaffney, P. R. J.; Driscoll, P. C.; Tabor, A. B. J. Org.
Chem. 2003, 68, 8185–8192.
Ca), 54.2 (Cys-Ca), 53.2 (OCH3), 38.4 (Phe-Cb), 28.3
(C(CH3)3), 27.01 + 27.00 (Cys-Cb); m=z (ESþ): 474.2
(M+Na)þ, 925.5 (2M+Na)þ; HRMS (ESþ): calcd for
C21H29N3O6SNa (M+Na)þ, 474.1669, found, 474.1671;
RP-HPLC: 14.7 min (ELSD).
5. Ring opening of b-lactones: (a) Shao, H.; Wang, S. H. H.;
€
Lee, C.-W.; Osapay, G.; Goodman, M. J. Org. Chem.
1995, 60, 2956–2957; (b) Shao, H.; Lee, C.-W.; Zhu, Q.;
Gantzel, P.; Goodman, M. Angew. Chem., Int. Ed. Engl.
1996, 35, 90–92.
12. Data for 5 after cleavage from resin and semi-preparative
RP-HPLC purification (16%); 1H NMR (DMSO-d6,
400 MHz): d 7.96 (d, 1H, J ¼ 9 Hz, Val-NH), 7.83 (d,
1H, J ¼ 8 Hz, Cys-NH), 5.43 (s, 1H, Dha-Hb), 5.11 (s, 1H,
Dha-Hb), 4.47 (m, 1H, Cys-Ha), 4.30 (m, 1H, Leu-Ha),
4.10 (m, 1H, Val-Ha), 3.95–3.40 (m, 7H, Pro-Ha + 2Pro-
Hd + 4Gly-Ha), 2.83–2.63 (m, 2H, Cys-Hb), 2.27 (t, 1H,
J ¼ 9 Hz, Cys-SH), 2.20–2.08 (m, 1H, Leu-Hb), 2.07–1.73
(m, 4H, Leu-Hb + Val-Hb + Pro-Hc), 1.64–1.45 (m, 2H,
Pro-Hb), 0.94–0.80 (m, 13H, Leu-CH3 + Val-CH3 + Leu-
Hc); 13C NMR (DMSO-d6, 100 MHz): d 171.8, 170.9,
170.6, 169.9, 168.9, 168.2, 165.0 (6CONH + CONH2),
137.2 (Dha-Ca), 104.5 (Dha-Cb), 59.9 (Leu-Ca), 58.2
(Val-Ca), 54.9 (Cys-Ca), 51.0 (Pro-Ca), 49.5 (Pro-Cd),
42.1 (Gly-Ca), 41.7 (Gly-Ca), 40.1 (Pro-Cb), 30.0 (Val-Cb),
€
6. Biomimetic addition: (a) Schmidt, U.; Ohler, E. Angew.
Chem., Int. Ed. Engl. 1976, 15, 42; (b) Toogood, P. L.
Tetrahedron Lett. 1993, 34, 7833–7836; (c) Probert, J. M.;
Rennex, D.; Bradley, M. Tetrahedron Lett. 1996, 37, 1101–
1104; (d) Crescenza, A.; Botta, M.; Corelli, F.; Santini, A.;
Tafi, A. J. Org. Chem. 1999, 64, 3019–3025; (e) Burrage,
S.; Raynham, T.; Williams, G.; Essex, J. W.; Allen, C.;
Cardno, M.; Swali, V.; Bradley, M. Chem. Eur. J. 2000, 6,
1455–1466; (f) Okeley, N. M.; Zhu, Y.; van der Donk, W.
A. Org. Lett. 2000, 2, 3603–3606; (g) Zhou, H.; van der
Donk, W. A. Org. Lett. 2002, 4, 1335–1338.
7. Mitsunobu reaction: see Ref. 4c.
8. Fukase, K.; Kitazawa, M.; Sano, A.; Shimbo, K.;
Horimoto, S.; Fujita, H.; Kubo, A.; Wakamiya, T.; Shiba,
T. Bull. Chem. Soc. Jpn. 1992, 65, 2227–2240.
29.4
(Leu-Cb),
26.1
(Cys-Cb),
24.6
(Pro-Cc),
23.5 + 22.6 + 21.8 + 19.2 + 18.1
(Leu-CH3 + Val-CH3 +
Leu-Cc); m=z (ESþ): 613.7 (M+H)þ; HRMS (ESþ): calcd
for C26H44N8O7S1Na (M+Na)þ, 635.2946, found,
635.2944; RP-HPLC (1220): 13.1 mins.
€
9. (a) Osapay, G.; Goodman, M. J. Chem. Soc., Chem.
Commun. 1993, 1599–1600; (b) Mayer, J. P.; Zhang, J.;
Groeger, S.; Liu, C.-F.; Jarosinski, M. A. J. Pept. Res.
1998, 51, 432–436.
13. Data for 6 after solid-phase cyclisation, cleavage and
purification by semi-preparative RP-HPLC purification
(33%); 1H NMR (DMSO-d6, 400 MHz): d 8.99 (d, 1H,
J ¼ 8 Hz), 8.75 (t, 1H, J ¼ 6 Hz), 8.18–8.02 (m, 3H), 7.94
(d, 1H, J ¼ 8 Hz), 7.59 (d, 1H, J ¼ 9 Hz), 7.19 + 6.97 (2s,
2H), 4.92 (m, 1H), 4.69–4.53 (m, 2H), 4.10 (m, 1H), 3.85–
3.55 (m, 5H), 3.54–3.43 (m, 1H), 3.34 (m, 1H), 2.97 (dd,
1H, J ¼ 15, 7 Hz), 2.86 (dd, 1H, J ¼ 14, 4 Hz), 2.69–2.54
(m, 2H), 2.27–2.12 (m, 1H), 2.00 (m, 2H), 1.85–1.70 (m,
2H), 1.71–1.43 (m, 3H), 0.94–0.77 (m, 12H); 13C NMR
(DMSO-d6, 100 MHz): d 172.9, 170.8, 170.7, 170.0, 169.3,
169.1, 168.8, 59.5, 58.0, 53.7, 50.7, 50.7, 46.9, 43.9, 41.7,
40.5, 34.0, 33.5, 31.5, 30.2, 23.5, 22.6, 22.0, 21.8, 19.2, 18.0;
m=z (ESþ): 613.3 (M+H)þ, 635.3 (M+Na)þ; HRMS (ESþ):
calcd for C26H45N8O7S (M+H)þ, 613.3127, found,
613.3123; RP-HPLC (k220): 11.7 min.
10. Matteucci, M.; Bhalay, G.; Bradley, M. Org. Lett. 2003, 5,
235–237.
11. Data for 2: Rf : 0.23 (Et2O/hexanes, 7/3); IR (neat): mmax
:
2570 (SH), 1736, 1686, 1656, 1629 cmÀ1 1H NMR
;
(CDCl3, 400 MHz): d 8.39 (br s, 1H, Dha-NH), 7.33–
7.10 (m, 5H, Phe-ArH), 7.00 (m, 1H, Cys-NH), 6.51 (s,
1H, Dha-Hb), 5.41 (s, 1H, Dha-Hb), 5.06–4.89 (br s, 1H,
Phe-NH), 4.85 (m, 1H, Cys-Ha), 4.56–4.33 (br s, 1H, Phe-
Ha), 3.81 (s, 3H, CO2CH3), 3.22–2.89 (m, 4H, Phe-
Hb + Cys-Hb), 1.38 (9H, C(CH3)3); 13C NMR (CDCl3,
100 MHz): d 170.8 (CO2Me), 170.6 (Phe-CONH), 163.7
(Dha-CONH), 155.5 (OCONH), 136.36 + 136.33 (Phe-
ipso-ArC), 133.5 (Dha-Ca), 129.3 + 128.9 (Phe-o +
m-ArCH), 103.4 (Dha-Cb), 80.6 (C (CH3)3), 56.7 (Phe-