Glyco- and peptidomimetics from three-component joullie-ugi coupling show selective antiviral activity

Article abstract of DOI:10.1021/ja043924l

Chlorination-elimination chemistry coupled with three-component Joullie-Ugi reaction and facile deprotection allowed efficient access to an array of polyhydroxylated pyrrolidines through parallel synthesis that may be considered to be a library of imino (

Full text of DOI:10.1021/ja043924l

Published on Web 12/17/2004
Glyco- and Peptidomimetics from Three-Component Joulli e´ -Ugi Coupling
Show Selective Antiviral Activity
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,‡
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Timothy M. Chapman, Ieuan G. Davies, Baohua Gu, Timothy M. Block, David I. C. Scopes,
Philip A. Hay,| Stephen M. Courtney, Luke A. McNeill, Christopher J. Schofield, and
,⊥
|,⊥
†
†
,
†
Benjamin G. Davis*
Chemistry Research Laboratory, UniVersity of Oxford, Mansfield Road, Oxford U.K., OX1 3TA, Drexel Institute for
Biotechnology & Virology Research, Drexel UniVersity, College of Medicine, 700 East Butler AVenue,
Doylestown, PennsylVania 18901, and Oxford Glycosciences Ltd, The Forum, 86 Milton Park,
Abingdon, Oxfordshire U.K., OX14 4RY
Received October 6, 2004; E-mail: ben.davis@chem.ox.ac.uk
Scheme 1. Joulli e´ -Ugi MCRa
The hydroxylated pyrrolidine scaffold provides valuable sources
1
2
not only of glycomimetics but also of hydroxyproline derivatives.
With the aim of creating biodivergently targeted libraries, we have
exemplified a multicomponent reaction (MCR) giving novel bis-
amide pyrrolidines accessed through a chlorination-elimination
3
strategy. Previous studies have shown such imines to be efficient
3
scaffolds for reaction with organometallic reagents. We demon-
strate here that they are also highly effective components in MCRs
that may be applied to library construction.
The mechanism proceeds via intermediates that are common to
4
5
the Ugi reaction, a widely used reaction in library construction.
However, the use of cyclic imine components in MCRs is rare: in
989 Joulli e´ demonstrated the role of a single cyanophenoxy
1
6
,7
dihydropyrrole. It is all the more surprising that such a “Joulli e´ -
Ugi” process has not been applied to hydroxylated cyclic scaffolds
as this would yield a ready route to compounds that could be
considered as either azasugars or dihydroxyprolyl peptides. The
motif thus formed would therefore potentially be effective in both
carbohydrate processing (e.g., glycosidase) and/or peptide-process-
ing (e.g., prolyl peptidase) inhibitors.1 Several important syntheses
a
(a) DBU, THF. (b) Carboxylic acid, isocyanide, MeOH. (c) 50% TFA,
THF.
,2,8
9
of dihydroxyproline modules have been reported; many highlight
Carboxylic acids i-ix and isocyanides A-H (Scheme 1) were
selected for a library.12 These included hydrophobic groups since
they have been shown to enhance the activity of inhibitors of
glycosidases, glucosylceramide synthase, and prolyl-processing
enzymes.8 Test arrays probed efficiency. Reaction of 1 with
N-acetyl glycine v and isocyanides A-H gave single diastereo-
isomers in total yields of 43-77%.15 1 plus acids i-ix with
isocyanide C gave 55-99% yield also as single diastereomers.
10
11
the difficulty, length, relatively low yields, and long reaction
times11 of prolyl amide coupling. Improved access to coupled
hydroxyprolines is desirable. We hereby report that entry to the
Joulli e´ -Ugi reaction through elimination followed by facile depro-
tection has allowed access to one of the most wide-ranging aza-
sugar/dihydroxyprolyl libraries,12 which in turn has yielded potent
inhibitors of two disease-associated targets, one based on inhibition
of carbohydrate processing and one on peptide processing.
Erythritol 3 and threitol 4 imines, formed from treatment of
N-chloramine precursors 1 and 2 (Scheme 1) with DBU established
the unoptimized viability of reaction with N-acetyl glycine v and
benzyl isocyanide D (Scheme 1), giving reasonable yields of
elaborated bisamide (68 and 64% yield over two steps from 1 and
,14
Similar studies on 2 gave similarly good to excellent yields (78-
5,16
9
1
(
8% with v1
plus A-H and 77-100% with C plus i-ix as a
15,17
:1 mixture of diastereoisomers).
TFA) proceeded quantitatively in most cases.15 Having established
Deprotection of all adducts
a good level of generality, the library was expanded to 132
deprotected members in total yields of 42-100% from erythritol
N-chloramine 1 and 77-100% from threitol N-chloramine 2, all at
2
, respectively); excellent diastereoselectivity (de > 98%) was
13
observed for erythritol 6vD. Deprotection with TFA proceeded
smoothly in 90% for erythritol 8vD and 62% for the 2,3-trans
threitol species 9vD. Conditions for ready parallel handling were
then established: isocyanides were removed in vacuo and acids
were removed by base wash, and final treatment with TFA afforded
pure deprotected product without recourse to chromatography.
1
15
>
90% purity as determined by LC-MS and H NMR.
More complex homochiral components were also tested, includ-
ing representative biomolecule fragments. (S)-sec-Phenethyl iso-
cyanide I and N-Ac-L-phenylalanine xi gave 51 and 59% yield and
>
98% de18 with viii and E, respectively. Disappointingly, proline,
deprotected glucuronic, and galacturonic acids gave little product.
Protection of sugar hydroxyls is typical in successful MCRs,
5
,19
†
University of Oxford.
‡
and gratifyingly, protected D-galacturonic acid x20 gave 44% overall
yield, >98% de (1 + x + E) of azadisaccharide mimic 9xE.
Having readily generated an array of potential glyco- and
peptidomimetics, we probed their activities against 15 different
Current address: Chemistry Dept., 80 St. George St., Toronto, Canada.
§
Drexel University.
Oxford Glycosciences Ltd.
Current address: Evotec OAI, 151 Milton Park, Abingdon, Oxon U.K.,
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OX14 4SD.
506
9
J. AM. CHEM. SOC. 2005, 127, 506-507
10.1021/ja043924l CCC: $30.25 © 2005 American Chemical Society

C O M M U N I C A T I O N S
(
3) (a) Chapman, T. M.; Courtney, S.; Hay, P.; Davis, B. G. Chem. Eur. J.
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Figure 1. Identified inhibitors of glucosylceramide synthase, bovine viral
diarrhoea virus, and anti-E2 Western assay of 9iiA-treated BVDV.
(
sugar- and peptide-based targets. To test glycomimicry, the library
was screened against five human glycosidases, five non-mammalian
glycosidases, and the glycosyltransferase glucosylceramide synthase
(
GCS), a Gaucher’s disease target.21 The entire library showed little
(9) (a) Taylor, C. M.; Weir, C. A. J. Org. Chem. 2000, 65, 1414. (b) Jenkins,
C. L.; Bretscher, L. E.; Guzei, I. A.; Raines, R. T. J. Am. Chem. Soc.
22
or no inhibition of glycosidases at 100 µM. This appears to be
due to requirement for a basic endocyclic nitrogen atom. Gratify-
ingly, treatment of 9iE with 1.5 equiv of lithium aluminum hydride
allowed the rarely performed chemoselective24 reduction of the
tertiary amide in the presence of the secondary amide at C-1 and
library elaboration;2 10 and 11 were successfully identified as GCS
inhibitors with IC50 117 and 140 µM, respectively (Figure 1).
Inhibitors of HIF hydroxylases are of current anti-ischemic inter-
est, and elastases are implicated in, e.g., pancreatitis, rheumatoid
arthritis, and emphysema. To test peptide mimicry, the library was
screened against peptide-processing target enzymes that preferen-
tially accept substrates that contain prolyl residues, FIH,27 PHD2,28
and porcine pancreatic elastase, but showed only low inhibition.15
Finally, the library was tested in whole pathogen assays against
hepatitis B virus (HBV) and bovine diarrhoea virus (BVDV), which
2003, 125, 6422. (c) Kalaus, G.; Malkieh, N.; Kajt a´ r-Peredy, M.; Brlik,
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23
2
001, 11, 2537. (b) Taylor, C. M.; Barker, W. D.; Weir, C. A.; Park, J.
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Chem. 1999, 64, 1554. (d) Fujii, M.; Miura, T.; Kajimoto, T.; Ida, Y.
Synlett 2000, 1046.
5
(
11) Typically no higher than ∼70% and up to 10 days. See ref 9.
(12) Albeit modest in comparison to other compound libraries, this is a
promising step for azasugars. For leading examples, see: (a) Saotome,
C.; Wong, C.-H.; Kanie, O. Chem. Biol. 2001, 8, 1061 (27 member). (b)
Wu, C.-Y.; Chang, C.-F.; Chen, J. S.-Y.; Wong, C.-H.; Lin, C.-H. Angew.
Chem., Int. Ed. 2003, 42, 4661 (60 members). (c) Gerber-Lemaire, S.;
Popowycz, F.; Rodr ´ı guez-Garc ´ı a, E.; Asenjo, A. T. C.; Robina, I.; Vogel,
P. ChemBioChem. 2002, 5, 466 (96 member).
26
(13) Interestingly, little selectivity (dr 1:1) was seen for threitol 7vD.
(
14) (a) Butters, T. D.; van den Broek, L. A. G. M.; Fleet, G. W. J.; Krulle T.
M.; Wormald, M. R.; Dwek, R. A.; Platt, F. M. Tetrahedron: Asymmetry
2
000, 11, 113. (b) Fernandez, J. H.; Hayashi, M. A. F.; Camrgo, A. C.
M.; Neshich, G. Biochem. Biophys. Res. Commun. 2003, 308, 219.
(
15) See Supporting Information for further details.
29,30
(16) The reaction with benzyl isocyanide gave an anomalous yield of 49%.
is a primary model of human HCV.
A specific pattern of potency
(
(
17) N-Methylpyrrole-2-carboxylic acid gave no Ugi product.
against BVDV for aromatic R1 and branched R2 substituents
emerged. IC50 values of 25 µM (9iiA) and 30 µM (9viiG, 9viiiF,
MOI ) 0.5, Figure 1) compare very favorably with NN-DNJ
18) No efficiency difference for either of the two enantiomers of imine 3.
(19) Lockhoff, O. Angew. Chem., Int. Ed. 1998, 37, 3436.
(
(
20) Godage, H. Y.; Fairbanks, A. J. Tetrahedron Lett. 2000, 41, 7589.
21) Sawkar, A. R.; Cheng, W.-C.; Beutler, E.; Wong, C.-H.; Balch, W. E.;
Kelly, J. W. Proc. Natl. Acad. Sci. U.S.A. 2002, 99, 15428.
(deoxynojirimycin), 10 µM, MOI ) 0.1 and better than those for
31
(22) This was unexpected since imino sugars with hydrophobic substituents
are inhibitors of GCS (see: Platt, F. M.; Neises, G. R.; Karlsson, G. B.;
Dwek, R. A.; Butters, T. D. J. Biol. Chem. 1994, 269, 27108) and
glycosidases (refs 3 and 8).
NB-DNJ (125 µM, MOI ) 0.1). Reduction of viral protein E2
level, lack of glycosidase, and HBV inhibition also indicated a
novel, selective mechanism distinct from those of these previous
imino sugars.31 We believe this to be the first example of a BVDV
inhibiting azasugar that does not affect HBV. Excitingly, no signi-
ficant toxicity was observed even at highest concentration (300 µM).
In conclusion, a rarely constructed azasugar/dihydroxy prolyl
array was assembled efficiently through three-component Joulli e´ -
Ugi reaction accessed using chlorination-elimination methodology
and allowed the identification of inhibitors of carbohydrate- and
peptide-processing targets, including disease enzyme GCS and
model viral pathogen BVDV.
(
23) Reduction with L-selectride or 9-BBN both proceeded sluggishly, even
at reflux, and no trace of the reduction product could be detected.
(24) Soai, K.; Ookawa, A. J. Org. Chem. 1986, 51, 4000.
(
25) Although selectivities for 10 vs 11 were poor, pleasingly and strikingly,
no reduction of the secondary amide was detected.
(26) Hewitson, K.; McNeill, L.; Schofield, C. J. Curr. Pharm. Des. 2004, 10,
821.
(
27) Factor inhibiting hypoxia-inducible factor, which catalyzes hydroxylation
of VNAP motifs. See: (a) Hewitson, K. S.; McNeill, L. A.; Riordan, M.
V.; Tian, Y. M.; Bullock, A. N.; Welford, R. W.; Elkins, J. M.; Oldham,
N. J.; Battacharya, S.; Gleadle, J. M.; Ratcliffe, P. J.; Pugh, C. W.;
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J.; Whelan, D.; Gorman, J.; Whitelaw, M. Science 2002, 295, 858.
28) Isoform of the prolyl hydroxylase domain containing hydroxylases. See:
(
(
a) Jaakkola, P.; Mole, D. R.; Tian, Y.-M.; Wilson, M. I.; Gielbert, J.;
Acknowledgment. We thank Dr. R. Donis, Nebraska, for the
kind gift of BVDV to T.M.B. and the EPSRC, BBSRC, The
Wellcome Trust, NIH (AI54764-01) and Oxford Glycosciences for
support.
Gaskell, S. J.; von Kriegsheim, A.; Hebestreit, H. F.; Mukherji, M.;
Schofield, C. J.; Maxwell, P. H.; Pugh, C. W.; Ratcliffe, P. J. Science
2
001, 292, 468. (b) Ivan, M.; Kondo, K.; Yang, H.; Kim, W.; Valiando,
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Ratcliffe, P. J. Nat. ReV. Mol. Cell. Biol. 2004, 5, 343.
Supporting Information Available: Experimental procedures and
characterization data for all library members and for biological testing.
This material is available free of charge via the Internet at http://
pubs.acs.org.
(
29) Zitzmann, N.; Mehta, A. S.; Carrou e´ e, S.; Butters, T. D.; Platt, F. M.;
McCauley, J.; Blumberg, B.; Dwek, R. A.; Block, T. M. Proc. Natl. Acad.
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