Synthesis and SAR studies of indole-based MK2 inhibitors

Article abstract of DOI:10.1016/j.bmcl.2008.01.119

Chemistry has been developed to specifically functionalize two structurally similar classes of indole-based MK2 inhibitors at positions prompted by a combination of X-ray crystallographic and computer assisted drug design. A gain in molecular potency was obtained by introducing aminomethyl groups to the lactam rings of 6-arylcarbamoyl-tetrahydro-β-carbolinone and 6-arylcarbamoyl-dihydropyrazino[1,2-a]indolone MK2 inhibitors. In addition, improvements in molecular potency were achieved by expansion of the lactam from a 6- to 7-membered ring leading to 7-arylcarbamoyl-tetrahydro-[1,4]diazepino[1,2-a]indolones.

Full text of DOI:10.1016/j.bmcl.2008.01.119

Available online at www.sciencedirect.com
Bioorganic & Medicinal Chemistry Letters 18 (2008) 1994–1999
Synthesis and SAR studies of indole-based MK2 inhibitors
Zhaoming Xiong,* Donghong Amy Gao, Derek A. Cogan, Daniel R. Goldberg,
Ming-Hong Hao, Neil Moss, Edward Pack, Chris Pargellis, Donna Skow,
Thomas Trieselmann, Brian Werneburg and Andre White
Research and Development, Boehringer Ingelheim Pharmaceuticals, Inc., 900 Ridgebury Road, Ridgefield, CT 06877, USA
Received 20 December 2007; revised 26 January 2008; accepted 29 January 2008
Available online 6 February 2008
This Paper is dedicated to Professor E. J. Corey on the occasion of his 80th birthday.
Abstract—Chemistry has been developed to specifically functionalize two structurally similar classes of indole-based MK2 inhibitors
at positions prompted by a combination of X-ray crystallographic and computer assisted drug design. A gain in molecular potency
was obtained by introducing aminomethyl groups to the lactam rings of 6-arylcarbamoyl-tetrahydro-b-carbolinone and 6-arylcar-
bamoyl-dihydropyrazino[1,2-a]indolone MK2 inhibitors. In addition, improvements in molecular potency were achieved by expan-
sion of the lactam from a 6- to 7-membered ring leading to 7-arylcarbamoyl-tetrahydro-[1,4]diazepino[1,2-a]indolones.
ꢀ 2008 Elsevier Ltd. All rights reserved.
Tumor necrosis factor alpha (TNFa) has been implicated
in many inflammatory diseases such as rheumatoid arthri-
tis (RA), inflammatory bowel disease, and psoriasis. To
date, several anti-TNFa biologics including Enbrelꢁ,
Remicadeꢁ, and Humiraꢁ have been approved for use
as anti-inflammatory therapies.1 Mitogen-activated pro-
tein kinase-activated protein kinase 2 (MK2) is a Ser/
Thr kinase that plays a critical role in the signal transduc-
tion pathway regulating the production of TNFa.2 It has
been reported2a that MK2 knockout mice challenged with
lipopolysaccharide produce significantly less TNFa than
the wild-type control mice. In addition, these MK2
knockout mice are resistant to disease in arthritis models.
Moreover, the MK2 knockout mice were reported to be
fertile and healthy.2a These reports suggest the inhibition
of MK2 may provide a safe and effective treatment of
TNFa mediated diseases.3
H
N
O
O
O
O
N
NH
NH
NH
NH
2
1
MK2 IC50: 1700 nM
N
N
O
MK2 IC50: 2700 nM
H
N
O
O
NH
O
N
NH
NH
NH
3
4
Ar
Ar
R
R
R: OH, NH2, substituted amines
Figure 1. SAR targets.
Recently we identified two series of structurally similar
indole-based MK2 inhibitors as exemplified by com-
pounds 1 and 2 (Fig. 1).4 An X-ray structure of a close
analogue of 1 revealed a number of polar residues (e.g.,
Asn191 and Asp207) in close proximity to the lactam
ring, suggesting that it may be possible to engage these
polar residues and further improve the potency of our
MK2 inhibitors. Molecular modeling indicated that a
polar group (e.g., CH2OH, CH2NH2) substituted at
3-position of the lactam ring as shown by general struc-
tures 3 and 4 may be able to pick up new interactions
with these polar residues (Fig. 2). In addition, the amine
group could be used as a functional handle (substituted
amines) to further explore SAR in this region. Herein we
report the synthesis and the SAR results of compounds
shown by general structures 3 and 45 and lactam ring-
expanded analogues (vide infra).
Keywords: MAPKAP-k2; MK2; b-Carbolinone; Pyrazino[1,2-a]indo-
lone; Diazepino[1,2-a]indolone.
*
Corresponding author. Tel: +1 203 798 4854; fax: +1 203 791
6072; e-mail: zhaoming.xiong@boehringer-ingelheim.com
0960-894X/$ - see front matter ꢀ 2008 Elsevier Ltd. All rights reserved.
doi:10.1016/j.bmcl.2008.01.119

Z. Xiong et al. / Bioorg. Med. Chem. Lett. 18 (2008) 1994–1999
1995
alcohol and azide displacement followed by ester hydro-
lysis provided 11. This allowed us to functionalize the
left part of the inhibitors first. Hydrogenation of the
azide group provided amines 3a and 3b. Alternatively,
substituted amines derivatives (e.g., 3e and 3f) could
be prepared from 10 by first ester hydrolysis and amide
coupling, and then mesylate formation and displace-
ment with aliphatic amines.
The syntheses of compounds exemplified by structure 4
(dihydropyrazino[1,2-a]indolones)10 proceeded through
two different routes (Schemes 2 and 3). Alkylation of in-
dole diester 12 with tosylate 13 provided diol 14 after ke-
tal group removal. Diol 14 was bis-mesylated and
displaced by azide to give diazide 15, which, when re-
duced11 by Me3P, cyclized in situ to form lactam 16.
Compound 16 was converted to primary amines 4a
and 4b by Boc-protection followed by ester hydrolysis,
amide coupling and Boc-deprotection. The synthesis
also allowed us to examine the effect of chirality through
preparing both enantiomers12 of 4a and 4b using enanti-
omerically pure tosylate 13.
Figure 2. Model of overlap of 2 (in green) with 4a (in yellow).
The synthesis of compounds exemplified by structure 3
(tetrahydro-b-carbolinones)6 is summarized in Scheme 1.
Methyl 2-formylindole-5-carboxylate 5 was first pro-
tected as benzyl carbamate 6. Knoevenagel condensa-
tion of 6 with ethyl nitroacetate provided a 1:1
mixture of E- and Z-olefins 7.7,8 Conversion to the ami-
no ester 8 was accomplished by NaBH4 reduction of the
double bond and hydrogenation of the nitro with simul-
taneous removal of the Cbz group. Treatment of amine
8 with triphosgene generated the corresponding isocya-
nate, which was converted to lactam 9 in situ when trea-
ted with 30% HBr in acetic acid.9 The aliphatic ester of 9
was selectively reduced by LiBH4 to give alcohol 10,
which served as a key intermediate. Mesylation of the
As shown in Scheme 3, substituted amines 4f–j were syn-
thesized from 12 through alkylation with 18 which was
prepared from racemic Boc-O-benzyl-serinol 19 through
cyclization with SOCl2 and oxidation with NaIO4 and
catalytic amount of RuCl3.13,14 Alkylation13 of 12 with
18 followed by Boc-deprotection and lactamization
afforded 20 in excellent yield. Ester hydrolysis and amide
coupling gave amide 21. Debenzylation of 21 with 30%
HBr in HOAc gave the acetate of the corresponding
alcohol, which was hydrolyzed to alcohol 4c. Substi-
tuted amines 4f–j were prepared from 4c by mesylation
and displacement with a variety of amines.
R
Cbz
H
N
N
e
N
c, d
NO2
b
O
O
O
NH2
NO2
O
O
O
O
H
CO2Et
CO2Et
CO2Et
7
8
5 R = H
a
6 R = Cbz
H
N
H
N
H
N
O
O
O
f
l, m
O
O
O
NH
NH
OH
NH
O
O
NH
NH
S
S
9
10
3d
CO2Et
OH
N
g, h, i
n, o
H
N
O
H
N
j, k
H
N
O
O
O
NH
O
O
N
NH
NH
NH
Ar
NH2
OH
11
3a Ar = 3-pyridyl
N3
R
3b Ar = 2-thiazolyl
3e R= NHMe
3f R = NMe2
Scheme 1. Reagents and conditions: (a) NaH, CbzCl, DMF, 0–23 ꢂC, 14 h, 84%; (b) nitroacetate, TiCl4, NMMO, THF, 0 ꢂC, 6 h, 85%; (c) NaBH4,
MeOH, 1 h; (d) H2, 10% Pd–C, HOAc–EtOH, 15 h, 75% over 2 steps; (e) triphosgene (0.4 equiv), Et3N, toluene–CH2Cl2 (1:2), 0 ꢂC, 1 h, then 30%
HBr in HOAc, 23 ꢂC, 2 h, 80%; (f) LiBH4, THF, 23 ꢂC, 6 h, 91%; (g) MsCl, Et3N, THF–DMA (2:1), 0–23 ꢂC; (h) NaN3, DMSO, 80 ꢂC, 12 h; (i)
NaOH, THF–MeOH, 70 ꢂC, 3 h, 58% over 3 steps; (j) ArNH2, HATU, HOAt, i-Pr2NEt, DMF, 50 ꢂC, 2 day, 85%; (k) H2, 10% Pd–C, DMA–MeOH,
2 h, 65%; (l) NaOH, THF–MeOH, 70 ꢂC, 2 h, 96%; (m) 2-aminothiazole, EDC, HOBt, i-Pr2NEt, DMAP, DMF, 50 ꢂC, 14 h, 58%; (n) MsCl, Et3N,
THF–DMA (2:1), 0–23 ꢂC, 2 h, 85%; (o) MeNH2 or Me2NH, DMSO, 100 ꢂC, 75%.

1996
Z. Xiong et al. / Bioorg. Med. Chem. Lett. 18 (2008) 1994–1999
CO2Et
N3
c, d
a, b
CO2Et
OH
e
CO2Et
TsO
O
O
N
O
O
N
N
H
O
O
O
O
O
14
O
N3
12
16
15
OH
13
O
O
O
f, g
h, i
O
N
N
NH
NH
O
N
NH
NH
Ar
OH
NH2
17
NH2
4a Ar = 3-pyridyl
4b Ar = 2-thiazolyl
NHBoc
Scheme 2. Reagents and conditions: (a) 13, K2CO3, DMF, 100 ꢂC, 36 h, 90%; (b) 3 N HCl (2 equiv), THF, 50 ꢂC, 1 h, 81%; (c) MsCl, Et3N, THF–
DME, 0 ꢂC, 1 h, 98%; (d) NaN3, DMSO, 90 ꢂC, 14 h; (e) Me3P, THF–H2O (5:1), 45% over the 3 steps; (f) Boc2O, Et3N, 14 h, 100%; (g) NaOH,
THF–MeOH, 70 ꢂC, 2 h, 98%; (h) 2-aminothiazole, EDC, HOBt, i-Pr2NEt, DMAP, DMF, 50 ꢂC, 14 h, 62%; (i) TFA, CH2Cl2, 16 h, 92%.
O
O
O
O
c, d, e
f, g
O
O
+
O
N
S
12
O
N
N
N
NH
NH
O
OBn
NH
S
O
18
OBn
OBn
20
21
4c
a, b
h, i
O
O
O
j, k
O
N
N
O
NH
O
HN
N
NH
NH
S
H
HO
OBn
N
NH
S
19
OH
R
4f-j
N
Scheme 3. Reagents and conditions: (a) SOCl2, pyridine, CH2Cl2, 0–23 ꢂC, 14 h, 98%; (b) RuCl3 (0.1 mol %), NaIO4, EtOAc–H2O, 0–23 ꢂC, 3 h,
92%; (c) NaH, 18, DMF, 0–23 ꢂC, 14 h; (d) TFA, CH2Cl2, 14 h; (e) K2CO3, EtOH, 80 ꢂC, 2 h, 99% over 3 steps; (f) NaOH, THF–MeOH, 70 ꢂC, 2 h,
95%; (g) 2-aminothiazole, EDC, HOBt, i-Pr2NEt, DMAP, DMF, 50 ꢂC, 14 h, 94%; (h) 30% HBr in HOAc, 23 ꢂC, 1.5 h; (i) K2CO3, MeOH–DMA,
23 ꢂC, 1 h, 88% over 2 steps; (j) MsCl, Et3N, THF–DMA (2:1), 0–23 ꢂC, 5 h, 64%; (k) RNH2, DMSO, 100 ꢂC, 25–44%.
In general, the aminomethyl group consistently im-
proves the MK2 potency for both series [3a vs 1, and
(R)-4a vs 2], with a more substantial effect observed in
the tetrahydro-b-carbolinone series (3). Our modeling
predicted that the (R)-enantiomers would be more likely
to engage either Asn191 or Asp207 than the (S)-enanti-
omers (Fig. 2). The SAR results are consistent with that
prediction [(R)-4a vs (S)-4a, (R)-4b vs (S)-4b]. The
hydroxylmethyl group also improves the potency com-
pared to the unsubstituted lactams, but not to the same
extent as the amine in the tetrahydro-b-carbolinone ser-
ies (3a vs 3c, and 3b vs 3d). However, in the other series,
the alcohol shows similar potency to the amine [(R)-4b
vs 4c], indicating subtle differences in the SAR between
the two series (vide infra). Methyl group15 itself does
not improve the potency (4d vs 2, and 4e vs 22) conform-
ing that a polar group (NH2, OH) is responsible for the
potency gains. Mono-methylation of the amino group is
tolerated (3e and 4f) while disubstitution or substituents
larger than a methyl are detrimental to potency (3f, 4g–
j). In addition, acylation of the amino group results in a
loss of the potency (4k) (Table 1).
Asn191. Due to synthetic feasibility, the effect of lactam
ring size was examined in the dihydropyrazino[1,2-
a]indolone core. This effect was firstly explored on the
unsubstituted lactams. The 7-membered lactams 23a
and 23b (tetrahydro-[1,4]diazepino[1,2-a]indolones)17
were synthesized from 12 by alkylation with acryloni-
trile, reduction with CoCl2/NaBH4,18 lactamization,
ester hydrolysis, and amide coupling (Scheme 4). Unex-
pectedly, the 7-membered lactam improved potency
over the 6-membered lactam by 4-fold (Table 2, 23a vs
2, and 23b vs 22).
Combining this result with the addition of the amino-
methyl group further improved potency by 5- to 10-fold
for this series (Table 2, 25a vs 23a, and 25b vs 23b). The
alcohol analogue 25c showed similar potency to the cor-
responding amine 25b, which is consistent with the SAR
of 6-membered lactams of this series (vide sufra). As be-
fore, we found that a methyl group does not have much
effect on the potency (23a vs 25d, and 23b vs 25e). Sub-
stitutions on the amine decrease the potency signifi-
cantly (25f–h). The acetamide 25i is much less potent
as well.
We next examined the effect of increasing the size of the
lactam by one carbon hypothesizing that this may affect
the position of the amine group and perhaps provide an
improved binding interaction with either Asp207 or
The syntheses of these compounds are summarized in
Scheme 5. The primary amines 25a,b were synthesized
by the same method described for compound 4a,b, using

Z. Xiong et al. / Bioorg. Med. Chem. Lett. 18 (2008) 1994–1999
Table 1. MK2 inhibition activity results for 6-membered lactams
1997
H
N
O
O
O
O
N
NH
NH
NH
NH
Ar
Ar
R
R
series A
series B
Entry
Compound
Series
Ar
R
MK2 inhibition, IC50 (nM)16
1
2
3
4
5
6
7
8
1
A
A
A
A
A
A
A
B
3-Pyridyl
3-Pyridyl
3-Pyridyl
H
2600
260
3a
3c
3b
3d
3e
3f
2
CH2NH2
CH2OH
CH2NH2
CH2OH
CH2NHMe
CH2NMe2
H
1200
140
2-Thiazolyl
2-Thiazolyl
2-Thiazolyl
2-Thiazolyl
3-Pyridyl
1000
210
>10,000
1700
10
11
12
13
14
15
16
17
18
19
20
21
22
23
(R)-4a
(S)-4a
4d
B
B
B
B
B
B
B
B
B
B
B
B
B
B
3-Pyridyl
3-Pyridyl
3-Pyridyl
R-CH2NH2
S-CH2NH2
CH3
320
2300
1200
1100
160
22
2-Thiazolyl
2-Thiazolyl
2-Thiazolyl
2-Thiazolyl
2-Thiazolyl
2-Thiazolyl
2-Thiazolyl
2-Thiazolyl
2-Thiazolyl
2-Thiazolyl
2-Thiazolyl
H
(R)-4b
(S)-4b
4c
R-CH2NH2
S-CH2NH2
CH2OH
1400
550
4e
CH3
4000
580
4f
4g
CH2NHMe
CH2NHEt
CH2NHPr
CH2NHi-Pr
CH2NMe2
CH2NHAc
3000
4000
>10,000
>10,000
6900
4h
4i
4j
4k
O
O
R
a, b, c
d
O
O
NH
NH
N
+
12
N
N
NH
Ar
OH
R = H or Me
24
R
R
23a, 23b, 25d, 25e
Scheme 4. Reagents and conditions: (a) BnMe3NOH (40% in MeOH), dioxane, 23 ꢂC, 18 h; (b) CoCl2, NaBH4, THF–MeOH, 0 ! 23 ꢂC, 2 h, then
70 ꢂC, 14 h; (c) NaOH, THF–MeOH, 70 ꢂC, 2 h, 54–70% over 3 steps; (d) ArNH2, EDC, HOBt, i-Pr2NEt, DMAP, DMF, 50 ꢂC, 14 h, 23–70%.
Table 2. MK2 inhibition activity results for 7-membered lactams
O
O
NH
N
( )n
NH
Ar
R
16
MK2 inhibition, IC50 (nM)
Entry
Compound
Ar
n
R
1
2
3-Pyridyl
3-Pyridyl
0
1
0
1
1
1
1
1
1
1
1
1
1
H
1700
270
1100
190
29
2
23a
22
H
3
2-Thiazolyl
2-Thiazolyl
3-Pyridyl
H
4
23b
25a
25d
25b
25c
25e
25f
25g
25h
25i
H
5
CH2NH2
CH3
6
3-Pyridyl
320
35
7
2-Thiazolyl
2-Thiazolyl
2-Thiazolyl
2-Thiazolyl
2-Thiazolyl
2-Thiazolyl
2-Thiazolyl
CH2NH2
CH2OH
CH3
8
52
9
530
690
560
310
1200
10
11
12
13
CH2NHMe
CH2NHEt
CH2NMe2
CH2NHAc

1998
Z. Xiong et al. / Bioorg. Med. Chem. Lett. 18 (2008) 1994–1999
O
O
O
O
O
j
a, b
O
O
O
O
N
N
H
O
N
OTs
O
O
O
12
O
HO
27
26
29
30
OH
O
HO
k, l, m
c, d, e
O
O
O
f, g, h, i
O
NH
NH
N
O
N
NH
N
NH
O
O
Ar
28
NH2
NH2
OH
25a Ar = 3-pyridyl
25b Ar = 2-thiazolyl
n, o
O
O
O
N
p, q
O
N
NH
N
NH
N
NH
S
NH
S
25f-h
25c
R
OH
Scheme 5. Reagents and conditions: (a) 26, K2CO3, DMF, 100 ꢂC, 20 h; (b) 3 N HCl (2 equiv), THF–H2O, 1 h, 75% over 2 steps; (c) MsCl, Et3N,
CH2Cl2, 23 ꢂC, 2 h; (d) NaN3, DMSO, 90 ꢂC, 16 h; (e) Me3P, THF–H2O, 23 ꢂC, 4 h, then added toluene, 100 ꢂC, 14 h, 72% over 3 steps; (f) Boc2O,
Et3N, 3 h, 100%; (g) NaOH, THF–MeOH, 70 ꢂC, 2 h, 95%; (h) ArNH2, EDC, HOBt, i-Pr2NEt, DMAP, DMF, 50 ꢂC, 14 h, 67–91%; (i) TFA,
CH2Cl2, 14 h, 88–96%; (j) TsOH, toluene, reflux, 32%; (k) MsCl, Et3N, CH2Cl2, 23 ꢂC, 2 h, 98%; (l) NaN3, DMSO, 90 ꢂC, 14 h, 94%; (m) Me3P,
THF–H2O, 23 ꢂC, 4 h, then, 100 ꢂC, 14 h, 79%; (n) NaOH, THF–MeOH, 70 ꢂC, 2 h, 75%; (o) 2-aminothiazole, EDC, HOBt, i-Pr2NEt, DMAP,
DMF, 50 ꢂC, 15 h, 36%; (p) MsCl, Et3N, THF–DMA (2:1), 0–23 ꢂC, 5 h; (q) RNH2, DMSO, 100 ꢂC, 34–44% over 2 steps.
alkylating reagent 26.19 For the synthesis of methyl-
P.; Wu, K. K.; Yang, S.; Hartmann, S. J.; Reitz, D. B.
Bioorg. Med. Chem. Lett. 2007, 17, 4657; (c) Anderson, D.
amine 25d, the two symmetric hydroxyl groups of 27
R.; Hegde, S.; Reinhard, E.; Gomez, L.; Vernier, W. F.;
were differentiated by lactonization and the remaining
Lee, L.; Liu, S.; Sambandam, A.; Snider, P. A.; Masih, L.
hydroxyl group was then converted to the azide by
mesylation and azide displacement. Reduction of the
Bioorg. Med. Chem. Lett. 2005, 15, 1587; (d) Hanau, C. E.;
Mershon, S. M.; Graneto, M. J.; Meyers, M. J.; Hegde, S.
azide and in situ lactamization (lactone-lactam ex-
change) upon heating yielded 30. Ester hydrolysis and
G.; Buchler, I. P.; Wu, K. K.; Liu, S.; Nacro, K. PCT Int.
Appl. WO 058176 A2, 2004.
amide coupling gave 25c, which was converted to 25f–h
by mesylation and amine displacement.
4. (a) Wu, J.-P.; Wang, J.; Abeywardane, A.; Andersen, D.;
Emmanuel, M.; Gautschi, E.; Goldberg, D. R.; Kashem,
M. A.; Lukas, S.; Mao, W.; Martin, L.; Morwick, T.;
Moss, N.; Pargellis, C.; Patel, U. R.; Patnaude, L.; Peet,
G. W.; Skow, D.; Snow, R. J.; Ward, Y.; Werneburg, B.;
White, A. Bioorg. Med. Chem. Lett. 2007, 17, 4664; (b)
Goldberg, D.; Choi, Y.; Cogan, D.; Corson, M.; Gao, D.;
Gruenbaum, L.; Joseph, D.; Kasham, M. A.; Mara, L.;
Miller, C.; Moss, N.; Netherton, M.; Pargellis, C. P.;
Pelletier, J.; Sellati, R.; Skow, D.; Torcellini, C.; Tseng, C.;
Wang, J.; Watsi, R.; Werneburg, B.; Wu, J. P.; Xiong, Z.
Bioorg. Med. Chem. Lett. 2008, 18, 938.
In summary, we developed chemistry to access polar
substitutions on the lactam portion of two series of in-
dole-based MK2 inhibitors. In doing so, we have been
able to improve the potency of both series through
either introduction of an aminomethyl group or lactam
expansion to a 7-membered ring. Furthermore, combin-
ing both of these features provides potent MK2 inhibi-
tors suitable for further evaluation.20
5 For the detailed SAR of aryl amides on the left part, see
Ref. 4a. For the SAR discussion here, two standard aryl
groups: 3-pyridyl and 2-thiazolyl are used.
References and notes
6. For the recent examples of synthesis of tetrahydro-b-
carbolinones, see (a) Hudlicky, T.; Rinner, U.; Finn, K. J.;
Ghiviriga, I. J. Org. Chem. 2005, 70, 3490; (b) Lius, S. V.;
Burguete, M. I. Tetrahedron 1991, 47, 1737; (c) Jeannin,
L.; Sapi, J.; Vassileva, E.; Renard, P.; Laronze, J.-Y.
Synth. Commun. 1996, 26, 1711.
7. (a) Lehnert, W. Tetrahedron 1972, 28, 663; (b) Fornicola,
R. S.; Oblinger, E.; Montgomery, J. J. Org. Chem. 1998,
63, 3528.
1. (a) Klinkhoff, A. Drugs 2004, 64, 1267; (b) Barry, J.;
Kirby, B. Expert Opin. Biol. Ther. 2004, 4, 975.
2. (a) Kotlyarov, A.; Neininger, A.; Schubert, C.; Eckert, R.;
Birchmeier, C.; Volk, H.-D.; Gaestel, M. Nat. Cell Biol.
1999, 1, 94; (b) Neininger, A.; Kontoyiannis, D.; Kotlya-
rov, A.; Winzen, R.; Eckert, R.; Volk, H.-D.; Holtmann,
H.; Kollias, G.; Gaestel, M. J. Biol. Chem. 2002, 277,
3065.
8. The yield of the Knoevenagel condensation with unpro-
tected indole 5 was low (25–40%).
9. Bracher, F.; Hildebrand, D. Liebigs Ann. 1992, 1315.
10. For the reported synthesis of dihydropyrazino[1,2-a]indol-
ones, see (a) Rover, S.; Adams, D. R.; Benardeau, A.;
Bentley, J. M.; Bickerdike, M. J.; Bourson, A.; cliffe, I. A.;
3. For reported MK2 inhibitors, see (a) Anderson, D. R.;
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15. Compounds 4d–e were prepared from 2-aminopropanol in
same way as compound 21 (Scheme 3).
16. MK2 IC50 values were determined by the same method
described in Ref. 4a.
17. For the reported synthesis of tetrahydro-[1,4]diazepi-
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19. Tosylate 26 was prepared from 2-(hydroxymethyl)-1,3-
propanediol by published procedures, see (a) Xu, B.;
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X.; Senelo, J.; Cattaneo, M.; Zigheeti, M. L.; Chen, A.;
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A. Tetrahedron 1991, 47, 1001.
20. Some of the compounds (e.g., 25a, b, c) were tested for
cellular efficacy in an assay measuring the inhibition of
LPS-induced TNFa production from THP-1 cell. All of
them show EC50 > 10 lM. As discussed in our previous
paper,4b this is probably due to the poor membrane
permeability of these compounds as indicated by low
permeability (e.g., 0.1 · 10ꢀ6 cm sꢀ1 for 25a and
0.6 · 10ꢀ6 cm sꢀ1 for 25b) in the parallel artificial mem-
brane permeability assay (PAMPA).
11. Knapp, S.; Jaramillo, C.; Freeman, B. J. Org. Chem. 1994,
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12. The e.e.s are >95% as determined on OD-H column under
chromatographic conditions: 25% (EtOH:MeOH:DEA,
1:1:0.1)/hexanes, 1 ml/min, 310 nm.
13. (a) Alker, D.; Doyle, K. J.; Harwood, L. M.; McGregor,
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14. The racemic starting material was prepared by mixing
equal amount of enantiomerically pure (R)- and (S)-19.