7812
D. V. Filippo6 et al. / Tetrahedron Letters 43 (2002) 7809–7812
Figure 2. Chromatogram obtained by eluting crude FZ-tagged 18 (0.5 mg), loaded on a Fluophase™ column, with a gradient of
trifluoroethanol in 0.05% aq. TFA. MS analysis showed that the product eluted as a broad peak at 21 min is peptide 18. The small
‘shoulder’ indicated with an asterisk is due to partial loss of a t-Bu protecting group in 18.
References
9. The TNBS test (Hancock, W. S.; Battersby, J. E. Anal.
Biochem. 1976, 71, 260–264) was used for the visualiza-
tion (red colour) of free amino groups. The more com-
mon Kaiser test (Kaiser, E.; Colescott, R. L.; Bossinger,
C. D.; Cook, P. I. Anal. Biochem. 1970, 34, 595–598),
which requires heating, gave false positive results due to
concomitant cleavage of the methyltrityl (Mtt) group
under the applied conditions and ensuing reaction
between ninhydrin and the o-NH2 group of lysine.
10. The Mtt-group (Aletras, A.; Barlos, K.; Gatos, D.; Kout-
sogianni, S.; Mamos, P. Int. J. Peptide Protein Res. 1995,
45, 488–496), which can be cleaved with 1% TFA, was
used for lysine side chain protection to offset potential
solubility problems inherent to partially protected
oligopeptides.
11. A typical procedure for the tagging of peptides: Fmoc-
deprotected peptide resin 11 (27 mg, 12 mmol) was swol-
len in NMP and suspended in 0.3 mL of the same
solvent, FZ-Cl (1) (31 mg, 50 mmol) was added followed
by DIPEA (15 mL, 85 mmol) and the suspension was
shaken for 1 h until a negative TNBS-test was obtained.
The resin was washed with NMP and DCM. Subse-
quently, the peptide was cleaved by washing of the resin
with 1% TFA in DCM (20 mL in 10 portions for 20 min)
and the bright yellow solution obtained was treated with
triisopropylsilane (250 mL) until the colour disappeared.
Extraction of the organic phase with water and lyophiliz-
ing of the water layer furnished tagged peptide 13 (TFA-
salt, 10 mg, 60%). ESI MS 1291.5 (M+H)+.
1. Merrifield, R. B. J. Am. Chem. Soc. 1963, 85, 2149–2154.
2. (a) Kent, S. B. H. Annu. Rev. Biochem. 1988, 57, 957–989;
(b) Fields, G. B.; Noble, R. L. Int. J. Peptide Protein Res.
1990, 35, 161–214.
3. (a) Merrifield, R. B.; Bach, E. B. J. Org. Chem. 1978, 43,
4808–4816; (b) Funakoshi, S.; Fukuda, H.; Fujii, N. J.
Chromatogr. 1993, 638, 21–27; (c) Ball, H. L. Int. J.
Peptide Protein Res. 1996, 48, 31–47.
4. (a) Luo, Z.; Zhang, Q.; Oderaotoshi, Y.; Curran, D. P.
Science 2001, 291, 1766–1769; (b) Luo, Z.; Williams, J.;
Read, R. W.; Curran, D. P. J. Org. Chem. 2001, 66,
4261–4266; (c) Curran, D. P.; Luo, Z. J. Am. Chem. Soc.
1999, 121, 9069–9072.
5. Chen, W. P.; Xu, L. J.; Xiao, J. L. Tetrahedron Lett.
2001, 42, 4275–4278.
6. Herrmann, W. A.; Brossmer, C.; Reisinger, C. P.; Reier-
meier, T. H.; Ofele, K.; Beller, M. Chem. Eur. J. 1997, 3,
1357–1364.
7. Keuning, K. J.; Evenhuis, N. Recl. Trav. Chim. Pays-Bas
1935, 54, 73–75.
1
8. Selected analytical data: 1: H NMR (200 MHz, CDCl3)
l 7.31 (m 4H); 5.27 (s 2H); 2.98–2.90 (m 2H); 2.25–2.43
(m 2H). 13C NMR (50.1 MHz, CDCl3) l 150.5 (CꢀO);
140.6 (CH); 131.9 (Cq); 129.5 (CH); 128.8 (CH); 73.1
(CH2); 32.75; (m CH2); 26.20 (br. CH2). ESI MS (m/z)
537 (M−CO2−Cl−)+.
12. Fluorous HPLC was performed on
a Fluophase™
column (100 mm×4.6 mm, part. size 5 mm, pore size
,
300 A, Keystone, USA) eluting (1.5 mL/min) peptide 13
1
first with 80:10:10 MeOH/H2O/1% aq. TFA over 2 CV
(column volumes), then with a gradient up to 90:10
MeOH/1% aq. TFA over 7 CV and finally with MeOH
for 10 CV. In the case of peptide 18 a gradient of
trifluoroethanol from 25% to 90% in 0.05% aq. TFA over
13 CV was applied.
2: H NMR (200 MHz, CDCl3) l 7.32 (d, J=9 Hz, 1H);
7.11 (m 2H); 5.31 (s 2H); 2.90 (m 2H); 2.38 (s, m 5H). 13
C
NMR (50.1 MHz, CDCl3) l 150.2 (CꢀO); 140.86 (Cq);
130.89 (CH); 130.71 (CH); 129.49 (Cq); 126.21 (CH);
71.63 (CH2); 32.3 (CH2); 26.14 (CH2); 18.84 (Me).
1
3: H NMR (200 MHz, CDCl3) l 7.47 (m 4H); 7.27 (dt,
4
13. No degradation of FEZ-tag could be detected by RP
HPLC analysis after treatment of peptide 16 with TFA/
H2O (98/2) for 1 h at 20°C.
14. For a recent example of a heavy-fluorous Z-based protec-
tion, see: Schwinn, D.; Bannwarth, W. Helv. Chim. Acta
2002, 85, 255–264.
J=16.1 Hz J (H, F)=2.2 Hz, 1H); 6.25 (dt, J=16.1 Hz
3J (H,F) 12.1 Hz, 1H); 5.31 (s 2H). 13C NMR (50.1 MHz,
3
CDCl3) l 150.8 (CꢀO); 138.9 (t, J (C, F)=9.9 Hz, CH);
135.4 (Cq); 134.6 (Cq); 129.3 (CH); 128.0 (CH); 115.6 (t,
2J=23 Hz, CH); 72.5 (CH2).
10: 1H NMR (200 MHz, CDCl3) l 7.88 (d, J=9 Hz, 1H);
7.08 (m 2H); 3.89 (s 3H); 2.96 (m 2H); 2.60 (s 3H); 2.37
(m 2H). Anal. calcd for C19H13F17O2: C, 38.27; H, 2.20.
Found: C, 37.99; H, 2.45.
15. Preliminary experiments indicated that
a
Z-based
fluoroalkylated tag containing two fluorophilic tails was
readily accessible via the Heck cross-coupling procedure.