"...the step from the laboratory to the patient's bedside...is extraordinarily arduous and fraught with danger." Paul Ehrlich
Acridine Alkaloids
Baran Group Meeting
Jonathan Lockner
Dyes to Drugs:
1
9
8
7
2
3
4
N
10
6
5
acridine
dibenzo(b,e)pyridine
2,3,5,6-dibenzopyridine
2,3-benzoquinoline
10-azaanthracene
Orange Dye
U.S. Patent 537723 A, April 16, 1895 (Swiss chemists)
Cancer Treatment Using Specific 3,6,9-Substituted Acridines
WO2006095139, September 14, 2006 (Neidle et al)
3,6,9 are the important positions of acridine drugs
flat (planar) aromatic, hydrophobic, pKa 5.6
colorless to light yellow crystals (mp 107-110 °C)
chromatography on basic alumina
irritating odor, lachrymator, carcinogenic, mutagenic
→ Bruce N. Ames (UC Berkeley) studied carcinogenesis/mutagenesis by
chemicals, including acridines (Science 1972, 176, 47)
MeO
H2N
Cl-
NMR:
9.09 8.19
7.64
7.89
N
8.22
13C
NMR:
135.8
HN
Cl
125.5
130.3
149.1
1870 → acridine isolated from coal tar (Carl Grabe & Heinrich Caro, BASF, Germany)
Grabe introduced "ortho", "meta", "para" nomenclature
1895 → "Orange Dye" patent; acridines being used as fabric dyes & biological staining agents
1912 → Ehrlich & Benda proposed use of acridines as antimicrobials (acriflavine/Trypaflavin/Gonoflavin)
Ehrlich (of Salvarsan "606" fame) first introduced idea of synthetic chemotherapy
1913 → Carl Browning identified proflavine, the neutral (non-methylated) version of acriflavine
1914-1918 → WWI; acridines as wound antiseptics in base hospitals on Western Front
1917-1946 → widespread clinical use of acridines as antibacterials during "antibacterial gap"
1939-1945 → WWII; quinacrine used in eastern theatres, in absence of quinine from Japanese-held Java
1946 → end of WWII, penicillins eclipse acridines
1970s → nitracrine/Ledarkin; amsacrine/Amsidyl for cancer treatment
present → anticancer, anti-AChE, antiprion, antinociceptive
H2N
N
NEt2
NHSO2Me
HN
OMe
129.5
128.3
N
NH2
acriflavine
126.6
1H
N
Me
NH2
N
quinacrine/Mepacrine/Atebrin
(antimalarial)
proflavine
"There is no exaggeration that [the
availabiilty of quinacrine] probably
changed the course of history."
L. J. Bruce-Chwatt
N
amsacrine/Amsidyl
(antileukemia)
1
9
8
7
2
3
Baran Group Meeting
4
N
10
6
Acridine Alkaloids
5
Acridine Isolation:
Commercial Availability of Acridines:
O
NH2
N
H
9(10H)-acridanone
$18.84/g
mp >300 °C
N
acridine
$3.23/g
mp 107-110 °C
Jonathan Lockner
marine:
a) tunicates & ascidians
b) sponges
c) sea anemones
CO2H
N
9-aminoacridine
$1.19/g
N
9-acridinecarboxylic acid
$21/g
O
N
N
H2N
acridine orange (AO)
$2.56/g
H2N
N+
Cl- Me
N
O
N
H
N
N
plant:
a) bark of Australian scrub ash tree
N
N
NH2
O
O
O
acridine yellow (AY)
$2.19/g
cystodytin A
acronycine
NH2
Acriflavine (Trypaflavin)
$0.87/g
H 2N
N
NH2
chrysaniline ("phospin")
dyes silk & wool yellow
H2N
N
benzoflavin
$25.91/g
NH2
staining with AO:
Acridine Biosynthesis:
HO
CO2H
OH
OH
+
NH2
anthranilic acid
(or equiv)
OH
phloroglucinol
(or equiv)
N
OH
2,4-dihydroxyacridine
Chem. Rev. 1993, 93, 1825
Adv. Het. Nat. Prod. Syn. 1992, 2, 377
Die Pharmazie 1970, 25, 777
Australian J. Sci. Research 1951, 423
1
9
8
7
2
3
Baran Group Meeting
4
N
10
6
5
Acridine Alkaloids
Jonathan Lockner
Using Acridine Dyes to Study Cellular Processes:
N
N
absorption: 440-480 nm (blue)
emission: 520-650 nm (green-red)
"metachromatic fluorochrome"
N
NH2
acridine orange (AO)
nucleic acid selective fluorescent dye
N
Useful for cell cycle determination: stain nucleic acids; flow cytometry
Hydrophobic → quickly diffuses into cell membrane, then complexes with DNA (green
fluorescence) and RNA (red fluorescence)
AO/EDTA mixture used for 1) denaturing dsRNA, and 2) binding ssRNA
Darzynkiewicz, Z. Methods in Cell Biology 1990, 33, 285
Jaroszeski, M. J. Methods in Molecular Biology 1998, 91, 10
Cl
HN
N
Cl
Br
N
N
O
H
9-amino-6-bromo-DACA
J. Med. Chem. 1999, 42, 536
acridinecarboxamide complexed with hexanucleotide d(CG(5-BrU)ACG)2
(CG-preferential behavior associated with acridine chromophore)
OMe
Cl
N
quinacrine mustard
fluorescence studies of plant, animal, human chromosomes
Science 1970, 170, 762
MeO
O2N HN
N
HN
N
Interaction of Acridines with DNA:
"Single action": 9-aminoacridine; quinacrine; acridine orange
1) intercalate DNA
"Dual action": quinacrine mustard
1) intercalate DNA
2) form covalent bond with DNA
Intercalative activity (and thus mutagenicity) can be 'designed out' of the aminoacridine profile
→ Appropriately substituted acridines maintain anticancer potency by instead interfering with
topoisomerase II enzyme (e.g. amsacrine stabilizes DNA/topo II "cleavable complex")
Lerman, L. S. Proceedings of the National Academy of Sciences 1963, 49, 94
J. Antimicrobial Chemotherapy 2001, 47, 1
Current Med. Chem. 2002, 9, 1655
N
nitracrine/Ledakrin
(antitumor)
J. Med. Chem. 1992, 35, 4832
MeO
NHSO2Me
amsacrine/Amsidyl
(antileukemia)
J. Med. Chem. 1974, 17, 922
NHSO2Me
NMe2
N N
HN
MeO
N
Me
CONHMe
asulacrine/amsalog/CI-921
(anticancer)
J. Het. Chem. 1989, 26, 1469
N
H
NO2
PZA/pyrazoloacridine
(antitumor)
J. Med. Chem. 1992, 35, 4770
1
9
7
2
3
Baran Group Meeting
Prager, R. H.; Williams, C. M. Science of Synthesis 2004, 15, 988
Demeunynck. M. Expert Opin. Ther. Patents 2004, 14, 55
Chiron, J.; Galy, J.-P. Synthesis 2004 313
Albert, A. The Acridines, 2nd ed.; Edward Arnold Ltd: London, 1966
8
6
N
10
4
Acridine Alkaloids
5
Usual Acridine Synthesis Methodology:
From quinomethanes:
CO2H
Ph
NH2
Cu
X
X
O
CO2H
!
CO2H
HO
Cu
N
H
!
2-carboxy-diphenylamine
Acridone
Ullmann-Jourdan
X = Halogen
Reduction
Cyclization: POCl3; H2SO4; PPA, etc...,
Reduction: Na, BuOH, !, etc...,
Oxidation: CrO3; NaOH aq.; FeCl3; HNO3, etc...
Ph
ZnCl2
OH
Cyclization
N
H
H2N
Jonathan Lockner
160 °C
4h
NH2
R1
OH
+
O
N
H
Friedländer:
HO
OH"
120 °C
4h
HO2C
OH
O-
NH3Cl
NaOAc
150 °C
88%
Ph
K2CO3
alumina
Cu, CuI
20%
OMe
Cl
K2CO3, Cu
H2N
CyOH, reflux
N
H
CF3
From acylated diphenylamines:
N
OMe
Cl
+
CO2Et
Cl
MeCN
80 °C, 36 h
43%
OMe
Goldberg:
CO2H
O
NH
O
OMe
CO2H
CO2Et
then NaOH
43%
+
N
O
+
O
N
O
Via aza-Diels"Alder (del Mar Blanco 2000):
NMe2
N
O
MeCN, 70 °C
O2N
+ H2N
H2N
N
N
Ph
Cl
N
H
O
O
O2N
improved by µW
(J. A. Seijas, M. P. Vazquez-Tato)
Mn(OAc)3
+ NC
120 °C
58%
O
POCl3
reflux, 1 h
N
OH
R2
Via radical reactions of quinones (Chuang 1990):
OH
Ullman 1906:
Br
ZnCl2
200-270 °C
N
H
Cl
+
N+
OR
O
O
R1
From diphenylamines and carboxylic acids (Bernthsen 1884):
OH
N
O
OH
R1
N+
RCO2H
O
R2
O
20 °C
N
H
Acridane
N
OH
CHO H2SO4 R1
NO2
N
HO
N
From nitroarenes (Tanasescu 1937):
Oxidation
Acridine
Pfitzinger 1886:
HO
NH
HO
Ph
Ph
H2N
Ph
I2, HI, h#
N
H
63 %
O
N
Ph
N
N
O
N
R2
1
9
8
7
2
3
Baran Group Meeting
4
6
N
10
Acridine Alkaloids
5
AcO
OH
OAc
OH
N
H
O
! N2
! CO
! HCl
64%
! CO2
NH
OH
N
Via arylation of phenylacetonitriles (Makosza 1973):
Cl
CN
N
H
dibenzazepine
Et
90% aq H2SO4
Et O2N
N+
PCl3
95%
N
90%
N3
I2
+
NH2
N
H
Cl
SOCl2
then
TsNNH2
H
TsN N
270-300 °C
6h
PhH
N
65 °C, 80 h
69%
ARKIVOC 2006, (xii), 111
N
H2SO4
(NH4)2S2O8
N
N
H
MeO
OMe
N
TMS
O
CHO
NaOH
N
H
N
H2NNH2
Cl
N
N
Li
MeO
THF, !70 °C
88%
O
KO2, DMSO
rt, 18 h
61%
mCPBA
59%
N N
HN
Cl Cl
120 °C, 1 h
100%
N
N+
O-
N
Cl
O
N
OH
+
AcOH, HCl
OMe
N
Acridine 10-oxides:
100 °C, 2 h
73%
Cl
NH
BF3•OEt2
N3
O
N
H
N
H
NH2
N
Via the McFadyen!Stevens Reaction:
CO2Me
N
CN
CHO
PbO2
240 °C
CH3OH
N
N+
Me
Me
Chem. Ber. 1964, 97, 2418
Substitution at 9-position:
iPrCO2H
AgNO3
N
H
From diarylamines (this example also shows that carbonyl can be generated after N-arylation):
NH2
X-
H2O
92%
N
350 °C
CH2OH
h"
Pd/C
5%
Photolysis or pyrolysis of aryl azides:
700 °C
Photoalkylation:
Dehydrogenation:
N
O95%
N
Tetrahedron 1969, 25, 1125
+
50 °C, 2 h
O2N
PTC
peracids
Et
Et CN
nBuCO2H
N
N
O
P
H
OH
H
I2, AcOH
Ring Contraction:
OH
nBu
h"
h"
O
H2SO4
O
Reductive Alkylation:
Ring Expansion:
N
Cl
N
N
Electrocyclizations:
Jonathan Lockner
NiCl2•2H2O, Li, biphenyl
64%
CN
KCN
K3[Fe(CN)6]
70 °C, 3 h
35%
N+
O-
1
9
8
7
2
3
4
Baran Group Meeting
6
N
10
Acridine Alkaloids
5
Drug Synthesis:
Jonathan Lockner
CO2H
CO2H H N
2
Cl
NaBH4
1. KCN
OMe
Cl
OH
CO2H
Cl
Cl
O
OMe POCl3
N
H
N
Ac
OMe
Cl
Cl
2. NaOH
N
H
Cl
N
Ac
PPA
P2O5
Zirkle et al J. Org. Chem. 1961, 26, 135
N
H
Cl
OPOx
Mietzsch et al U.S. Patent 1938, 2113357
1. H2
OMe
Bayer 1932
important WWII drug;
cf. quinine
Cl
N
NEt2
HN
NEt2
H 2N
N
OMe
Cl
N
N
H
Cl 2. Me2N(CH2)3Cl
NaH
NMe2
Cl
Cl
quinacrine/Mepacrine/Atebrin
(antimalarial)
O
NMe2
NMe2
O
ClMg
NMe2
Cl
H2
Cl
H2NOC
CONH2
O
N
H
O
!
N
H
N
H
N
H
NH2
NaNH2
Bielavsky Collect. Czech. Chem. Commun. 1977, 42, 2802
NH2
chlomacran
(antipsychotic)
Zirkle U.S. Patent 1964, 3131190
Cl
N
H
H2SO4
NaOH
N
NMe2
O
N
H
N
N
NMe2
Holm Br. Patent 1963, 933875
CONH2
Br2
N
tacrine/Cognex
(antidementia)
acetone
O
O
Cl
N
H
N
H
chlorimipramine
(antidepressant)
dimetacrine
(antidepressant)
CN
O
HO
NH2
NH O
CuCl
N
H
N
Shutske, G. M.; et al J. Med. Chem. 1988, 31, 1278
Lednicer, D. Strategies for Organic Drug Synthesis and Design,
John Wiley & Sons, New York, 1998, pp. 383-387
NH2 OH
hydroxyl improves
oral absorption
N
velnacrine
(antidementia)
LiAlH4
NH2 O
N
Cl
1
9
8
2
7
3
4
Baran Group Meeting
N
10
Me
Jonathan Lockner
N
2. H2SO4, 86%
CO2H
Acridine Alkaloids
O
1. K2CO3, Cu, CuBr
NMP, 160 °C, 98%
CO2H
+
Cl
NH2
6
5
Me
N
H
COR
N
H
N
HN
OMe
Cl
99%
N
N
CONHMe
Me
asulacrine/amsalog/CI-921
(anticancer)
J. Het. Chem. 1989, 26, 1469
COR
R=Cl
N
MeNH2
H2O!CHCl3
R=NHMe
N
N
Cl
N,N-dimethylaniline MeO
!, 18 h
+
Cl
NH2
N
H
83%
NO2
MeO
H2NHN
NMe2
O
N
H
NO2
PZA/pyrazoloacridine
(antitumor)
J. Med. Chem. 1992, 35, 4770
N
H
N
N
N
HO
OMe
(!)-TAN-67
(antinociceptive)
" opioid receptor agonist
tacrine-PIQ hybrid
(fM AChE inhibitor)
Sharpless "click"
J. Am. Chem. Soc.
2005, 127, 6686
(+) isomer induced hyperalgesia
(opposite effect!)
NMe2
HN
NO2
Cl
MeO
THF!MeOH
rt, 7.5 h
89%
N
Cl
POCl3,
N,N-dimethylaniline
1,2-DCE, reflux, 1 h
88%
NMe2
N N
HO2C
Ph
H
OMe
NH
HO2C
quinpramine
(antiprion)
(for Creutzfeldt!Jakob disease)
intron splicing agent
Bioorg. Med. Chem.
1997, 5, 1185
Cl
aniline
HCl, CHCl3!NMP
MeO
N
N
NHSO2Me
HN
Me
HN
N
H
SOCl2, DMF
MeO
N
NO2
O
N
O
N
H
N
N
H
N
BRACO-19
telomerase inhibitor
Neidle et al. J. Med. Chem. 2003, 46, 4463
N
1
9
8
7
2
3
Baran Group Meeting
4
N
10
6
Acridine Alkaloids
5
Jonathan Lockner
Natural Product Synthesis:
Amphimedine
Nakahara, Heterocycles 1988, 27, 2095
Amphimedine
Stille, J. Am. Chem. Soc. 1988, 110, 4051
MeO
O
N
H
MeO
pTs2O MeO
2,6-lutidine
DMAP
CH2Cl2
92%
OSO2CF3
MeO
MeO
Pd(PPh3)4
A, LiCl
N
MeO
R=t-BuOCO
R=CF3CO
NH2
NHCOCF3
(A)
O
O
EtO
N
O
O
TBDMSO
N
O
N
1. B, dry acid-free
CHCl3, rt
2. MeOH, 64%
1. 6M HCl, THF
2. Me2SO4, K2CO3
DMF, 84%
0 °C
77%
Cl
NO2
O
N
O
NHCOCF3
O
N
N
O
N
N
O
O
amphimedine
(26% overall)
N
H
MeO
O
PCl5 MeO
POCl3
NO2
NO2
66%
N
Cl
MeO
MeO
N
H
O
1. B, CHCl3, 35 °C; H+
2. MeI, K2CO3, DMF, 7%
O
OTBDMS
Ghosez's diene (B)
O
MeO
CAN
CH3CN!H2O
NO2
NHCOCF3
O
O
140 °C
"quant"
80% H2SO4, 75 °C
53%
N
2. pyr•HF
48%
NO2
1. TFA
2. TFAA
DIPEA, THF
94%
1. B, THF, rt
HN
cat. pyridine
MeO
PhMe
O
MeO
CAN
CH3CN!H2O, rt
85%
NHBoc
SnMe3
O
NO2
+
1,4-dioxane
100 °C
87%
N
MeO
NHR
Cl
H2, Pd/C
Et3N
MeOH, rt
13%
N
N
O
N
N
O
amphimedine
(0.25% overall)
O
OTBDMS
N
H
unprecendented [4+2]
N
O
N
S
MeO
O
Michael
O
N
N
[4+2]
N
S
O
kuanoniamine A
Nakahara, Tetrahedron 1997, 53, 17029
Hepburn, Heterocycles 2006, 68, 975
S
O
1
9
8
7
2
3
Baran Group Meeting
4
For other pyridoacridines, see Chem. Rev. 1993, 93, 1825
6
N
10
Acridine Alkaloids
5
Jonathan Lockner
Natural Product Synthesis:
Ascididemin (X=H) and 2-Bromoleptoclinidinone (X=Br)
Bracher, F. Heterocycles 1989, 29, 2093
Bracher, F. Liebigs Ann. Chem. 1990, 205
O
O
X
+
NH2
O
CeCl3•7H2O
EtOH
N
20 °C, 16 h
62-78%
O
O
X
N
H
X
N
O
from
bottom left
N
H2SO4!AcOH (1:10)
reflux, 10 min
90-94%
O
N
1. HC(OEt)2NMe2
DMF, 120 °C, 1 h
AcO
N
O
ascididemin (X=H)
2-bromoleptoclinidinone (X=Br)
HONH3Cl
CH3CN
N3
AcO
reflux
56%
OEt
N
N3
O3, MeOH, !78 °C;
then Me2S, 77%
N3
2. NH4Cl, AcOH, reflux X
1 h, 59-69%
N3
N3
O
N
N
H
AcO
1. isopropenyl acetate, cat TfOH
2. DDQ, PhMe, reflux, 15 min
N3
AcO
3. NaHCO3, H2O!MeOH, rt, 12 h
40%
O
N
OH
N
O
"ketone"
(KO3S)2NO, MeOH
phosphate buffer, rt, 56%
Ascididemin
Moody, C. J.; Rees, C. W.; Thomas, R. Tetrahedron Lett. 1990, 31, 4375
I
O
N
2-iodoaniline
Et3Al
HO
N
HN
CH2Cl2
79%
I
BaMnO4
O
H2SO4
N
h"
32%
CH2Cl2
83%
N
N
N3
N
AcO
ascididemin
(see above)
reflux
80%
N
O
H
N
R
OHC
O
1. 10% NaOH, EtOH, 0 °C
2. Ac2O, pyridine, 88%
N3
N
AcO
!N2
O
HO
N
N
N
N
O
N3
CH2=CHOEt
1,2-DCE
cystodytin A (R=
Yb(fod)3
reflux
99%
cystodytin B (R=
cystodytin C (R=
N
O
Ac2O, pyridine, 99%
or Tf2O, DIPEA, CH2Cl2,
90%
AcO
O
+
N N
N
O
O
AcO
N3
AcO
N
The Cystodytins
Ciufolini, M. A.; Byrne, N. E. J. Am. Chem. Soc. 1991, 113, 8016
HO
O
PhMe
RO
R=OAc O
R=OTf
OH
N
triflate proved entirely resistant to Ortar deoxygenation;
successful completion of NPTS required rerouting from "ketone"
(more PG operations; amide moieties introduced much earlier)