C O M M U N I C A T I O N S
Scheme 2. Completion of the Synthesisa
Scheme 3. Reactions Catalyzed by PBP1b (Top) and PBP1a
(Top and Bottom)a
a Lipid II is proposed to add to the reducing end of the growing glycan
chain, as shown in the top depiction.13
II and Lipid IV substrates to probe the mechanisms of PGTs, and
more detailed studies are underway.
Acknowledgment. This research was supported by the NIH
(Grant GM076710).
Supporting Information Available: Experimental procedures and
spectral data for all compounds; enzyme expression, purification, and
reaction conditions. This material is available free of charge via the
a Conditions: (a) (NH2CH2)2, THF/CH3CN/EtOH (1:2:1), 60 °C; (b)
Ac2O, MeOH/H2O (5:1), room temp, 75% two steps; (c) NaH, S-(-)-2-
bromo-propionic acid, THF, 0 °C to room temp; (d) TMSCHN2, benzene/
MeOH (3:1), 0 °C, 70% two steps; (e) NIS, CH3CN/H2O (5:1), room temp,
75%; (f) 1H-tetrazole, (i-Pr)2NP(OBn)2, CH2Cl2, -40 to -20 °C; (g)
mCPBA, CH2Cl2, -40 °C to room temp, 84% two steps; (h) TBAF, THF,
0 °C to room temp; (i) 1.3 M KOH, THF/H2O (10:1), room temp, 64%
two steps; (j) HATU, DIEA, DMF, room temp, 60%; (k) Pd(OH)2/C, H2,
44%; (l) ammonium heptaprenyl phosphate, 1,1′-carbonyl diimidazole, THF,
room temp, then 16, SnCl2, DMF, room temp, 50%; (m) TBAF, DMF,
room temp, 69%; (n) (CH314CO)2O, toluene/16 mM NaOH in MeOH
(1:1), sonication, 37 °C, 50%.
References
(1) Walsh, C. Antibiotics: actions, origins and resistance; ASM Press:
Washington, DC, 2003; pp 23-51.
(2) Ostash, B.; Walker, S. Curr. Opin. Chem. Biol. 2005, 9, 459-466.
(3) (a) Ye, X. Y.; Lo, M. C.; Brunner, L.; Walker, D.; Kahne, D.; Walker, S.
J. Am. Chem. Soc. 2001, 123, 3155-3156. (b) Schwartz, B.; Markwalder,
J. A.; Wang, Y. J. Am. Chem. Soc. 2001, 123, 11638-11643. (c)
VanNieuwenhze, M. S.; Mauldin, S. C.; Zia-Ebrahimi, M.; Winger, B.
E.; Hornback, W. J.; Saha, S. L.; Aikins, J. A.; Blaszczak, L. C. J. Am.
Chem. Soc. 2002, 124, 3656-3660. (d) Breukink, E.; van Heusden, H.
E.; Vollmerhaus, P. J.; Swiezewska, E.; Brunner, L.; Walker, S.; Heck,
A. J. R.; de Kruijff, B. J. Biol. Chem. 2003, 278, 19898-19903.
(4) Peptidoglycan fragments lacking the diphospholipid moiety have been
prepared. See (a) Hesek, D.; Lee, M. J.; Morio, K. I.; Mobashery, S. J.
Org. Chem. 2004, 69, 2137-2146. (b) Inamura, S.; Fujimoto, Y.;
Kawasaki, A.; Shiokawa, Z.; Woelk, E.; Heine, H.; Lindner, B.; Inohara,
N.; Kusumoto, S.; Fukase, K. Org. Biomol. Chem. 2006, 4, 232-242.
(5) Denome, S. A.; Elf, P. K.; Henderson, T. A.; Nelson, D. E.; Young, K.
D. J. Bacteriol. 1999, 181, 3981-3993.
Table 1. Percentage of Peptidoglyan Formed from 14C-Lipid IV
(17)a
enzyme
(nM)
time
12C 1b
M)
14C 17
M)
% conversion to
peptidoglycanb
(min)
(
µ
(
µ
(6) (a) Chen, L.; Men, H.; Ha, S.; Ye, X. Y.; Brunner, L.; Hu, Y.; Walker, S.
Biochemistry 2002, 41, 6824-6833. (b) Ha, S.; Chang, E.; Lo, M. C.;
Men, H.; Park, P.; Ge, M.; Walker, S. J. Am. Chem. Soc. 1999, 121, 8415-
8426.
(7) (a) Castropalomino, J. C.; Schmidt, R. R. Tetrahedron Lett. 1995, 36,
5343-5346. (b) Debenham, J. S.; Madsen, R.; Roberts, C.; Fraser-Reid,
B. J. Am. Chem. Soc. 1995, 117, 3302-3303.
(8) (a) Gildersleeve, J.; Pascal, R. A.; Kahne, D. J. Am. Chem. Soc. 1998,
120, 5961-5969. (b) Taylor, J. G.; Li, X.; Oberthu¨r, M.; Zhu, W.; Kahne,
D. E. J. Am. Chem. Soc. 2006, 128, 15084-15085.
(9) There are scattered reports of other chemical glycosylations involving
partially protected glycosyl donors, see: (a) Raghavan, S.; Kahne, D. J.
Am. Chem. Soc. 1993, 115, 1580-1581. (b) Lopez, J. C.; Agocs, A.; Uriel,
C.; Gomez, A. M.; Fraser-Reid, B. Chem. Commun. 2005, 5088-5090.
(c) Plante, O. J.; Palmacci, E. R.; Andrade, R. B.; Seeberger, P. H. J. Am.
Chem. Soc. 2001, 123, 9545-9554. (d) Boons, G. J.; Zhu, T. Synlett 1997,
809-811. (e) Schmidt, R. R.; Toepfer, A. Tetrahedron Lett. 1991, 32,
3353-3356. (f) Tanaka, H.; Adachi, M.; Tsukamoto, H.; Ikeda, T.;
Yamada, H.; Takahashi, T. Org. Lett. 2002, 4, 4213-4216. (g) Ye, X.
S.; Wong, C. H. J. Org. Chem. 2000, 65, 2410-2431. (h) Green, L.;
Hinzen, B.; Ince, S. J.; Langer, P.; Ley, S. V.; Warriner, S. L. Synlett
1998, 440-442. (i) Hanessian, S.; Lou, B. L. Chem. ReV. 2000, 100,
4443-3363.
84 (PBP1b)
84 (PBP1b)
84 (PBP1b)
86 (PBP1a)
86 (PBP1a)
86 (PBP1a)
90
360
10
90
360
10
0
0.4
0.4
0.32
0.4
0.4
undetectable
undetectable
40.8
27.9
46.0
0
4
0
0
4
0.32
51.1
a All the experiments were carried out in the presence of penicillin G to
prevent peptide crosslinking. For experimental procedures, see Supporting
Information. b Conversion is based on utilization of 14C-labeled 17.
of SnCl2 as a Lewis acid accelerated the coupling reaction and
improved the yield significantly.10 Finally, global deprotection of
the silyl groups led to the desired target, heptaprenyl-Lipid IV
(2b). This compound was treated with 14C-acetic anhydride to make
*Lipid IV (17) to assay enzymatic activity.
*Lipid IV was incubated with either E. coli PBP1a or PBP1b
(Table 1), and reactions were analyzed as described previously.11
PBP1b did not utilize Lipid IV as a substrate unless Lipid II was
also included in the reaction mixture (Table 1).12 This result is
consistent with the accepted mechanism for transglycosylation, in
which Lipid II subunits are added sequentially to a growing polymer
chain (Scheme 3, top). Surprisingly, however, PBP1a was able to
convert Lipid IV to peptidoglycan polymer in the absence of Lipid
II (Scheme 3, bottom), showing that Lipid II is not an obligatory
substrate for all PGTs. This result suggests that the biological
functions of some PGTs may include coupling peptidoglycan
oligomers. The work reported here demonstrates the utility of Lipid
(10) Walker, D. A. Ph.D. Thesis, Princeton University, 2004, 55-93.
(11) (a) Anderson, J. S.; Matsuhashi, M.; Haskin, M. A.; Strominger, J. L.
Proc. Natl. Acad. Sci. U.S.A. 1965, 53, 881-887. (b) Leimkuhler, C.;
Chen, L.; Barrett, D.; Panzone, G.; Sun, B. Y.; Falcone, B.; Oberthu¨r,
M.; Donadio, S.; Walker, S.; Kahne, D. J. Am. Chem. Soc. 2005, 127,
3250-3251. (c) Barrett, D. S.; Chen, L.; Litterman, N. K.; Walker, S.
Biochemistry 2004, 43, 12375-12381. (d) Chen, L.; Walker, D.; Sun,
B.; Hu, Y.; Walker, S.; Kahne, D. Proc. Natl. Acad. Sci. U.S.A. 2003,
100, 5658-5663.
(12) Control experiments carried out with 14C-labeled N-acetylated Lipid II
showed that both enzymes convert this substrate to peptidoglycan polymer,
establishing that acetylation of the lysine amines does not prevent substrate
recognition by the PGTs.
(13) van Heijenoort, J. Glycobiology 2001, 11, 25R-36R.
JA069060G
9
J. AM. CHEM. SOC. VOL. 129, NO. 11, 2007 3081