Table 1 Synthesis of the nucleopeptide esters 8–12 and their selective
deprotection with lipase from Aspergillus niger (AA = amino acid, B
= nucleobase)
71–74%; iv, N-allyloxycarbonyl amino acid methyl ester phosphor-
oamidate, tetrazole, room temp., then ButOOH, 0 °C, 68–82%.
1 B. A. Juodka, Nucleosides Nucleotides, 1984, 3, 445; J. C. Wang, Annu.
Rev. Biochem., 1985, 54, 665; A. B. Vartapetian and A. A. Bogdanov,
Progress Nucleic Acids Res. Mol. Biol., 1987, 34, 209; T. J. Kelly,
M. S. Wold and J. Li, Adv. Virus Res., 1988, 34, 1.
Coupling
Yield (%)
Deprotection
Yield (%)
Entry AA1 AA2
AA3
B
2 Review: M. Salas, Annu. Rev. Biochem., 1991, 160, 39; L. Blanco,
J. M. La´zaro, M. de Vega, A. Bonnin and M. Salas, Proc. Natl. Acad.
Sci. USA, 1994, 91, 12198.
3 For a recent review on the synthesis of nucleotides which also adresses
the problems encountered in the removal of the blocking functions, see
S. L. Beaucage and R. P. Iyer, Tetrahedron, 1992, 48, 2223.
4 B. Juodka, V. Kirveliene and P. Povilionis, Nucleosides Nucleotides,
1982, 1, 497; E. Kuyl-Yeheskiely, P. A. M. van der Klein, G. M. Visser,
G. A. van der Marel and J. H. van Boom, Recl. Trav. Chim. Pays-Bas,
1986, 105, 69.
1
2
3
4
5
Ser
Ser
Ser
Ser
Thr
Gly
Glu (All)
Phe
Val
Phe
Asp (All) C
10
11
12
13
14
61
62
75
69
71
15
16
17
18
19
70
58
70
59
63
—
C
C
C
A
—
Phe
—
Aspergillus niger at pH 7 and 37 °C the C-terminal carboxylic
acid was smoothly deprotected (Scheme 1, Table 1). In the case
of these multifunctional, complex peptide conjugates, too, the
enzymatic transformations occured without any undesired side
reaction, i.e. neither the acetate, N-terminal urethane, allyl
phosphate, phenylacetamide and peptide bonds, nor the acid-
labile purine nucleoside and the extremely base-labile serine
phosphates were attacked. The biocatalyst again tolerated the
presence of purine and pyrimidine bases and different amino
acids and amino acid sequences in the nucleopeptides. Its
substrate specificity guaranteed that the allyl esters which were
employed for masking of the amino acid side chain functions in
10 and 11 were not removed either. By means of this enzymatic
protecting group technique the desired selectively unmasked
nucleopeptides 15–19 were obtained in high yield. Nucleopep-
tide 15 represents the characteristic linkage region of the
nucleoprotein of adenovirus 2,12 and 16 is derived from the
nucleoprotein of bacteriophage Ø 29.13
Overall, the enzymatic protecting group strategy and the set
of orthogonally stable blocking groups described here open a
route to the construction of complex and sensitive nucleopep-
tides by means of a flexible building block strategy. The ready
accessibility of these multifunctional peptide conjugates may
serve to develop new tools for research at the interface between
chemistry and biology.
This work was supported by the Bundesministerium fu¨r
Bildung und Forschung, the Boehringer Mannheim GmbH and
the Fonds der Chemischen Industrie.
5 E. Kuyl-Yeheskiely, C. M. Tromp, A. W. M. Lefeber, G. A. van der
Marel and J. H. van Boom, Tetrahedron, 1988, 44, 6515; E. Kuyl-
Yeheskiely, C. M. Dreef-Tromp, A. Geluk, G. A. van der Marel and
J. H. van Boom, Nucleic Acids Res., 1989, 17, 2897; C. M. Dreef-
Tromp, J. C. M. van der Marel, H. van den Elst, G. A. van der Marel and
J. H. van Boom, Nucleic Acids Res., 1992, 20, 4015; Y. Ueno, R. Saito
and T. Hata, Nucleic Acids Res., 1993, 21, 4451; J. Robles, E. Pedroso
and A. Grandas, Tetrahedron Lett., 1994, 35, 4449; J. Robles,
E. Pedroso and A. Grandas, J. Org. Chem., 1994, 59, 2482; J. Robles,
E. Pedroso and A. Grandas, Nucleic Acids Res., 1995, 23, 4151.
6 Reviews: (a) H. Waldmann and M. Schelhaas, Angew. Chem., 1996,
108, 2192; Angew. Chem., Int. Ed. Engl., 1996, 35, 2056; (b)
H. Waldmann and D. Sebastian, Chem. Rev., 1994, 94, 911; (c)
T. Kappes and H. Waldmann, Liebigs Ann. Recl., 1997, 803.
7 H. Waldmann and A. Reidel, Angew. Chem., 1997, 109, 642; Angew.
Chem., Int. Ed. Engl., 1997, 36, 647; H. Waldmann, A. Heuser and
A. Reidel, Synlett 1994, 65-67.
8 For the enzymatic removal of methyl esters from glycosylated amino
acids, see D. Cantacuzene, S. Attal and S. Bay, Bioorg. Med. Chem.
Lett., 1991, 1, 197; S. Attal, S. Bay and D. Cantacuzene, Tetrahedron,
1992, 48, 9251; H. Ishii, K. Unabashi, Y. Mimura and Y. Inoue, Bull.
Chem. Soc. Jpn., 1990, 63, 3042.
9 M. Dessolin, M.-G. Guillerez, N. Thieriet, F. Guibe´ and A. Loffet,
Tetrahedron Lett., 1995, 36, 5741.
10 For the undesired attack of proteases on peptide bonds in the course of
enzymatic removals of blocking functions from peptides see the
references given in ref. 6(b), in particular: E. Walton, J. O. Rodin,
C. H. Stammer and F. W. Holly, J. Org. Chem., 1962, 27, 2255; G. Kloss
and E. Schro¨der, Hoppe-Seylers Z. Physiol. Chem., 1964, 336, 248.
11 For the enzymatic removal of MEE esters from glycosylated amino
acids and glycopeptides, see J. Eberling, P. Braun, D. Kowalczyk,
M. Schultz and H. Kunz, J. Org. Chem., 1996, 61, 2638.
12 J. E. Smart and B. W. Stillmann, J. Biol. Chem., 1982, 257, 13499.
13 J. M. Hermoso and M. Salas, Proc. Natl. Acad. Sci. USA, 1980, 77,
6425; J. M. Hermoso, E. Mendez, F. Soriano and M. Salas, Nucleic
Acids Res., 1985, 13, 7715.
Footnote and References
† Synthesis of 1–3: i, Me3SiCl (6 equiv.), pyridine, room temp., then
PhCH2COCl (3 equiv.), 1-hydroxybenzotriazole (2 equiv.), MeCN–
pyridine (2:1), room temp., then conc. NH3,
0 °C, 87–92%; ii,
4,4A-dimethoxytrityl chloride (1.2 equiv.), pyridine, room temp., then Ac2O
(6 equiv.), DMAP, 81–89%; iii, ZnBr2, MeNO2, room temp., 10 min,
Received in Glasgow, UK, 16th June 1997; 7/04215I
1862
Chem. Commun., 1997