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Microwave-Accelerated Palladium-Catalyzed Organic and Medicinal Chemistry
Mats LarhedDivision of Organic Pharmaceutical Chemistry
Department of Medicinal ChemistryUppsala University Sweden
Microwave UGMNovember 7, 2007
Copenhagen
Disposition
• Introduction• Carbonylations• Oxidative Heck reactions – Pd(II)• Heck reactions – Pd(0)• HIV-1 protease inhibitors• Acknowledgement
2007 - the Carl von Linnaeus Tercentenary
An Improved in situ Amino-Carbonylation Protocol with Mo(CO) 6 as a solid CO Source
• Cr(CO)6 80%• Mo(CO)6 84%• W(CO)6 77%• Fe3(CO)12 0%• Co2(CO)8 28%
• DBU mediated CO release
• Improved method with sluggish amines and amino acids
• ArCl work with [( t-Bu)3PH]BF 4 and Herrmann’s pallada-cycle
Wu et al. Organometallics 2006, 1434Lagerlund et al. J. Comb. Chem. 2006, 4Wu et al. Org. Lett 2005, 3327Wannberg et al. J. Org. Chem. 2003, 5751Wan et al. J. Comb. Chem. 2003, 82Wan et al. J. Org. Chem. 2002, 6232Kaiser et al. J. Comb. Chem. 2002, 109
FAB-MS
M(CO)6 Yield
X
Mo
O
O
OO
O
O
HNR'R''
Mo
N
N
OO
O
O
N
N
O
NR'R''
2 CO
[Pd], Mo( CO)6
Air, 15 minDBU, THF
+
10 equiv DBU+
R RX = I, Br, Cl39 examples35-95%
Aminocarbonylation or Heck Reaction with Allylamine?
• No competing Heck reaction
R
I NH2
Mo(CO)6, Pd(OAc) 2
DBU, DioxaneMW, 125 oC, 10 min
R
NH
O
R
Br
NH2R
NH
OPPd
o-tolo-tol
OAc
[(t-Bu)3PH]BF4, Mo(CO)6
DBU, Dioxane
dimer
MW 140 oC, 15 min
R
Cl
NH2R
NH
OPPd
o-tolo-tol
OAc
[(t-Bu)3PH]BF4, Mo(CO)6
DBU, Dioxane
dimer
MW 160 oC, 20 min
66-81%8 Examples
66-80%10 Examples
55-78%8 Examples
Appukuttan et al. Submitted
Me
NH
O
NH
O
NH
O
HN
O
MeO
NH
O
NH
O
NH2
OS
HN
NH
O
O
O
HNO
NH NH
O
HN
O
OMe
OMe
NH
O
HN
O
O
HNNH
O
OO
HN
OS
HN
O2N
N
NH
O
NH2
NH
O
NHMe
Scale-Up of Aminocarbonylation
• 0.4 mMol scale in 3 mL dioxane (81%)• 2.0 mMol scale in 10 mL dioxane (78%)• 25.0 mMol scale in 125 mL dioxane (80%)• Direct scalability• No problem with Mo(CO) 6, 4 bars pressure
I
MeO
NH
O
MeO
H2N
Mo(CO)6, Pd(OAc) 2
DBU, Dioxane
MW, 125 oC, 10 min
Appukuttan et al. Submitted
Aminocarbonylations of Aryl Triflates in Neat Water
• Under development• Mo(CO)6 as a solid CO-source• X-Phos needed• Only small amounts of benzoic acid generated
Odell et al. In preparation
OTfH N
R2
R1
R
H2NOTfOTf
X-Phos, Na 2CO3
OTf
R
HN
NR1
R2
O
Mo(CO)6, Palladacycle
H2O, MW, 175 oC, 40 minYield 36-72 %
+
2
Hepatitis C Virus (HCV)
• 170 million infected
• 3-4 million newly infected/year
• Primary indication for liver transplantations
• Urgent need for better therapies
Sandström et al.
Development of Novel Peptidomimetic HCV Protease Inhibitors
Other substituents
N
O
O
HN
ONH
N
O
O
O
HN
O
SO
O
Ki = 0.025 nMEC50 = 0.93 nM
Ongoing Lampa, ÅkerblomCyclization (metathesis)
NH
O
O
Unnatural amino acid
Örtqvist et al. Bioorg. Med. Chem. 2007, 15, 1448-1474
Ongoing
variation of the acyl sulfonamide function!
Rönn et al. Bioorg. Med. Chem. 2006, 14, 544-559
Rönn et al. Submitted
aromatic backbone
Rönn et al. Submitted
To be continued
heterocyclic backbone
Ongoing Örtqvist, Gising
ββββ-amino acidsOngoing Nurbo
Sandström et al.
Synthesis of Acyl Sulfonamides with Mo(CO) 6
O
NH
OS
O O
O
IH2N
SO O
INH
OS
O O
INH
OS
O O
I
Ph
O
NH
OS
O O
F3C
I
F3C
NH
OS
O O
S I NH
OS
O O
S
S
I
NH
OS
O O
S
H2NS
O O
NH
OS
O O
H2NS
O O
Br
NH
OS
O O
Br
H2NS
O ONH
OS
O O
H2NS
O O
CF3
NH
OS
O O
CF3
NH
OS
O OI
NH
OS
O O
Ph
O
Entry Iodide Sulfon amide Pr oduct Isolated yield (%)
188
87
88
80
70
76
88
65
79
88
84
72
71
2
3
4
5
6
7
8
9
10
11
12
13
I
HNS
O O14 N
OS
O O
47
NH
OS
O OBr
H2NS
O O
Br
F
F
F
F3C
NH
OS
O O
BrNH
OS
O O
S Br NH
OS
O O
S
NH
OS
O OBr
NC
NH
OS
O O
NC
Br
H2NS
O O
H2NS
CF3
O O
NH
OS
O O
NH
OS
CF3
O O
Entry Bromide S ulfonamide Product Isolated yield (%)
1
2
3
4
5
6
7
8
9
10
11
O
Br
O
NH
OS
O O
Br
O
NH
OS
O O
O
Br
NH
OS
O O
93
94
91
93
95
96
95
83
79
88
80
ArX
H2NS
R
O O
NH
SR
O O
Ar
O
+microwaves15 min
[Pd], Mo(CO) 6
DBU, dioxane
Wu et al. J. Org. Chem. 2005, 3094
Synthesis of a Hepatitis C Virus NS3 Protease Inhibitor
O
NH
BocHN SO O
Br
N
O
N
O
O
OH
OBocHN
NH
O
SO
O
N
O
N
O
O
HN
OBocHN
ONH
SO
O
O
NH
BocHN SO O
HN
OS
O O
1. HCl/1,4-dioxane
2. HBTU, DIEA, DMF
[Pd], Mo(CO) 6
DBU, dioxane
microwaves 15 min
H2NS
O O
K i-value of 85 ± 7 nM
52%
76%
Wu et al. J. Org. Chem.2005, 3094
HCV Full-length NS3(protease-helicase/NTPase)
H2N BrN
OBocHN
O
N
O
O
NH
N
OBocHN
O
N
O
O
NH
R1
R2
Br
Br
H2NBr
R1
R2
N
OBocHN
O
N
O
O
NH
N
OBocHN
O
N
O
O
HN
ONH
R1
R2
SOO
O
NH
S RO O
Microwaves140 oC, 15 min
RSO2NH2Herrmann's palladacycle
Fu salt, Mo(CO) 6, DBU1,4-dioxane
ortho (77%)meta (63%)para (82%)
ortho, R=phenyl (35%), 830 nMmeta, R=phenyl (44%)para, R=phenyl (35%)ortho, R=methyl (50%), 5900 nMortho, R=cyclopropyl (62%)ortho, R=benzyl (56%)ortho, R=4-methoxyphenyl (43%)ortho, R=4-(trifluoromethyl)phenyl (42%), 310 nMortho, R=2-thienyl (37%)
R1=CH3, R2=H (76%)R1=H, R2=CF3 (88%)
R1=CH3, R2=H (45%), 3200 nMR1=H, R2=CF3 (35%), 310 nM
HATU, DIEACH2Cl2, 45 oC
POCl3, pyridine-15 oC to rt
Microwaves140 oC, 15 min
PhSO2NH2Herrmann's palladacycle
Fu salt, Mo(CO) 6, DBU1,4-dioxane
N
OBocHN
O
N
O
O
OH
Novel HCV Protease Inhibitors by Amidocarbonylation
Rönn et al. Submitted
Preparative Advances and Lessons Learned
• Mo(CO)6 serves as a reliable solid CO liberator both with classic heating and microwave heating
• Inter- and intramolecular Pd(0)-catalyzed amino-, am ido-, hydrazido- and alkoxycarbonylations proceed smoothly in organic solvents, fluorous solvents or water
• Aryl iodides, -bromides, -chlorides and –triflates are all good substrates
• The methodology is useful for lead optimization• Limitation: The reaction mixture must be directly s ealed
after addition of Mo(CO) 6 and efficiently stirred
NH
HN
OH
OH
O
O
O
O
I
I
O
OSi
Si
NH
HN
OH
OH
O
O
O
OO
OSi
Si
NH2
O
H2N
O66%
Mo(CO)6, [(t-Bu) 3PH]BF 4Palladacycle, DIEA, DBUNH2OH x HCl , Dioxane
MW, 120 oC, 20 min
M. Larhed: Microwave-promoted carbonylations. Modern Carbonylation Methods , L. Kollár, Ed. Wiley-VCH, In Print
3
The Oxidative Heck Reaction
R Ar B(OH)2[Pd(II)] R
Ar
+ + Pd(0)
Reoxidation
R Ar X[Pd(0)] R
Ar
+
The Oxidative Heck Reaction:
The Heck Reaction:
Richard F. Heck
Heck
Pd(0) Pd(II)
Pd(0)
R1
B(R2)2
OxidativeHeck
Ar1 X
Ar1
R1
Ar2
R1
Suzuki
Ar1 Ar2
Ar2
Oxidative Heck Reactions
• Boronic acids readily undergo trans-metallation
• Which reoxidant to use?
• Very few mechanistic studies
• Microwave scale-up?
Relation between the classic Heck reaction, the oxidative Heck reaction and the Suzuki coupling
Andappan et al. Mol. Div. 2003, 97, Enquist et al. J. Org. Chem. 2006, 8779, Andappan et al. J. Org. Chem. 2004, 5212, Enquist et al. Green Chemistry 2006, 338.
H3C
B(OH)2
N
OPd(OAc) 2, dmphen
N
O+NaOAc, MeCN, air, rt
Reaction Investigated with ESI-MS
• Electron-rich olefin• NaOAc as base• Samples for ESI-MS removed during reaction
Enquist et al. J. Org. Chem. 2006, 8779
N N
2,9-dimethyl-1,10-phenanthroline (dmphen)
The palladium acetate catalyzed dmphen-modulated ox idative Heck reaction in acetonitrile with an electron-rich olefin. Cationic intermediates in the catalytic cycle are assigned letters from A–C.
The Plausible Catalytic Cycle of the Oxidative Heck Reaction
N
O N
O
NN
N
NPdN
PdNN
NN
PdOAc
N N
N
O
N
N
C
PdN
N
N
PdOAc
N
N
N
PdN
HN
H2O2
O2 (Air)
A
B
(HO)2B
N N
+
+
=
2,9-dimethyl-1,10-phenanthroline (dmphen)
Base-Free Oxidative Heck
PdN
N NH• Homocoupling intermediate detected by ESI-MS
• Produced from the p-Tolyl-Pd intermediate and p-Tolyl boronic acid
• Small amount biaryl side-product observed in all Oxidative Heck reactions
• Base needed for Suzuki-type biaryl formation• Base screen showed no need for base in Oxidative
Heck• Jung reported the base-free Oxidative Heck during
our studies (Jung et al. J. Am. Chem. Soc. 2006, 16384) with O 2 as oxidant
• Can we perform this chemistry with air instead of O 2?• Improved chemoselectivity? Microwaves?
Base-Free Oxidative Heck
• Reactions at room temperature: Open vessel charged with boronic acid, n-butyl acrylate, Pd(OAc) 2 (0.02 equiv), dmphen(0.024 equiv) and acetonitrileunder vigorous stirring
• Reactions at elevated temperatures: Microwave-transparent vessel charged with boronic acid, n-butyl acrylate, p-benzoquinone (0.5 equiv), Pd(OAc) 2 (0.02 equiv), dmphen(0.024 equiv), acetonitrile, sealed under air and exposed to microwave irradiation
• Scale-up at room temp from 1 mmol to 50 mmol scale
n-Bu
B(OH)2
n-Bu
CO2Bu
B(OH)2O
O
CO2BuO
O
B(OH)2HOCO2Bu
HO
B(OH)2 CO2Bu
Ac
B(OH)2
Ac
CO2Bu
B(OH)2
O
CO2Bu
O
F3C
B(OH)2
F3C
CO2Bu
MeO
B(OH)2
MeO
CO2Bu
B(OH)2 CO2Bu
1 rt100
24 h10 min
8486
2 rt100
18 h10 min
4968
3rt100rt
18 h10 min18 h
979497
4 rt100
24 h10 min
8385
5 rt100
48 h10 min
9050
6 rt100
24 h10 min
9389
7 rt100
72 h10 min
9290
8 rt100
48 h10 min
9577
9 rt100
48 h10 min
7095
CO2Bu ArB(OH) 2
Pd(OAc) 2 ArCO2Budmphen
+
_______________________________________________________________entry boronic acid product T (°C) t yield (%)_______________________________________________________________
Lindh et al. J. Org. Chem. 2007, 7957
4
Base-Free Oxidative
Heck rt100
rt120
24 h1 h
9874
N
O
rt100
O
rt100
CO2Bu rt100
rt100
rt100
Ac
CO2Bu
CO2Bu
N
O
Ac
N
O
O
Ac
O
CO2Bu
Ac
CO2Bu
1
3
2
4
6
__________________________________________________________________________________________________________________________
Reactions at room temperature: Open vessel charged with boronic acid, olefin, Pd(OAc) 2 (0.02 equiv),
dmphen (0.024 equiv) and acetonitrile under vigorou s stirring. Reactions at elevated temperatures:
Microwave-transparent vessel charged with boronic a cid, olefin, Pd(OAc) 2 (0.02 equiv), dmphen (0.024
equiv), p-benzoquinone (1.0 equiv), acetonitrile, sealed und er air and exposed to microwave irratiation.
5
7
entry olefin product T (°C) t yield (%)
24 h10 min
8577
192 h20 min
7979
24 h10 min
7175
24 h10 min
8237
48 h10 min
9388
120 h10 min
2286
Ph
PhS
O O
rt100
N
O
Ac
O
O
Ac
O
rt100
PhS
O O
O
O
rt100
rt100
rt100
rt100
rt100
Ph
Ph
Ac
12
14
8
9
10
13
15
ααααββββ
ααααββββ
240 h10 min
8769
48 h10 min
7595
240 h10 min
596
24 h10 min
9178
120 h10 min
1538
72 h10 min
7094
72 h10 min
7094
entry olefin product T (°C) t yield (%) a__________________________________________________________________________________________________________________________
B rt100
B11 24 h10 min
6769O
O
O
O
CO2BuCO2Bu Batch Scale-Up of Oxidative Heck
O
O
O
OB(OH)2
B(OH)2
O
O
O
O
O
O
Pd(OAc) 2 (2 mol%)dmphen (2.4 mol%)
p-benzoquinone (60 mmol) MeCN, 100 °C, 20 min50 mmol 100 mmol
50 mmol 100 mmol
91%
87%
Pd(OAc) 2 (2 mol%)dmphen (2.4 mol%)
p-benzoquinone (60 mmol) MeCN, 100 °C, 20 min
+
+
• From 0.5 mmol to 50 mmol • p-Benzoquinone as palladium reoxidant• Advancer instrument• Air as reoxidant instead of O 2 or p-
benzoquinone?
dmphenNN
Lindh et al. J. Org. Chem. 2007, 7957
Batch Scale-Up of Oxidative Heck with Air as Reoxidant
O
O
O
OB(OH)2
B(OH)2
O
O
O
O
O
O
Pd(OAc) 2 (2 mol%)dmphen (2.4 mol%)
Air (4 bar), MeCN
50 mmol 100 mmol
50 mmol 100 mmol
95%
88%
100 °C, 20 min
Pd(OAc) 2 (2 mol%)dmphen (2.4 mol%)
Air (4 bar), MeCN100 °C, 20 min
+
+
• Air introduced via vessel entry port• Air as reoxidant worked fine
Lindh et al. J. Org. Chem. 2007, 7957
• A multitude of available new palladium catalysts (o r precatalysts)• Palladacycles, pincer complexes, encapsulated polyu rea polymers ......• Not much known regarding the structure of catalytic ally active species at hhigh temperature (microwave conditions) • Pd(II)/(IV) mechanism or sophisticated Pd(0) sources? Compare with old-hfashioned Pd(OAc) 2, Pd2(dba)3, Pd/C •• hEnCat 30, EnCat Pd(0)
PPd
O O
o -Tolo -Tol
O
O PPh2
PPh2
Pd OCF3
O
PdN
O
O
2
2
Modern Palladium Catalysts at High Temperature (Microwave Conditions)
Nilsson and Sjöberg et al. Submitted
Per Sjöberg
Herrmann et al J. Organomet. Chem. 1999, 23 Heck et al. J. Org. Chem. 1975, 2667
Bedford et al. New J. Chem. 2000, 745Jones et al. J. Catal. 2004, 101
• Design of experiments:• Bidentate ligand-controlled regioselective cationic Heck harylation reaction• Oxidative addition intermediates detected by ESI-MS analysis hof ongoing microwave heated reaction mixture - in ac cordance hwith Pd(0) catalysis by Pd(0) release from Pd sourc e• Internal αααα-product selectivity support Pd(0)-catalysis ( αααα/ββββ-ratio)
ArOTfAr Pd L
L OR
MW
Ar
O
Ar
OR
Pd(0)
L L
ESI-MSdetectionPd source
+ L L
H2O
ααααββββ
ORAr
+αααα
ββββ
Modern Palladium Catalysts at High Temperature (Microwave Conditions)
Nilsson and Sjöberg et al. Submitted
Catalysts as Pd(0) Sources at 150 oC
P P
P P
Ph2P PPh2
ArOTfAr Pd P
P OnBu
150 oC 1 h, MW
P PAr
OnBu
OnBuAr
Pd(0)
Ar = 1-Naphthyl
+
ααααββββ
+
αααα-product ββββ-product(120 oC)
=
PPd
O O
o-Tolo-Tol
O
O PPh2
PPh2
Pd OCF3
O
PdN
O
O
Pd(OAc) 2
2
2
Pd2(dba)3
EnCat 30EnCat Pd(0)
Yes -
Yes
Yes
Yes
Yes-
87 071 0
71 0
82 0
67 0
82 067 0
5
Examples of ESI-MS Detected Cationic Catalytic Intermediates
P PArOTf
Ar Pd PP OnBu
150 oC 1 h, MW
Ph2P PPh2P PP
PdO O
o-Tolo-Tol
Pd
Ph2P
ArPh2P
Ph2PPPh2(II)
PPd
Ph2P PPh2(II)
Ar
OnBu
Pd
Ph2P
ArPh2P
Ph2PPPh2
O
(II)(o-Tol)2
2
+
ααααββββ
αααα-product(120 oC)
Pd(0)
= Ar = 1-Naphthyl or 4-CN-Ph
PP
Intermediates detected in an ongoing Heck reaction and verified by isotopic pattern, MS-MS and use of different ligands and aryl triflates NN Ph2P PPh2
• Pd(II)-based Palladacycles and Pincer complexes und ergo hstructural cleavage upon bidentate ligand coordinat ion hfollowed by a reduction and release of ”Pd(0)”• The bidentate ligand-controlled Heck reaction proce eds via the hidentical oxidative addition complex and deliver ex clusively thehαααα-product regardless of the Pd source• Commercially available encapsulated Pd catalysts (P d EnCat 30 hand EnCat Pd(0) show similar behavior• We conclude that it is unlikely that the investigat ed reactionshproceed via a Pd(II)/Pd(IV) redox cycle• All investigated catalysts (precatalysts) serve as useful Pd(0)hsources
Modern Palladium Catalysts at High Temperature (Microwave
Conditions)
Nilsson and Sjöberg et al. Submitted
Peter Nilsson
ON
ON+
OHN
O1) PTSA, HC(OMe)3
2)
39%
, HCl (g)
3) distillation 35%Separable on silica
• Utilizing the chiral pool
• Scope and limitation
ON
Ar-Cl
Pd( t-Bu 3P)2
O PdN
H
Ar
Cl ON
Ar
HCl (aq)O
Ar
(R)-2-Aryl-2-methyl-cyclopentanonesee?
Asymmetric Chelation-Assisted Heck Arylation with Aryl Chlorides
Nilsson et al. J. Am. Chem. Soc. 2003, 3430, Datta et al. Submitted
O PdN
H
A r
X
O
NH Ar
X
Pd
• Preferred Si-face addition furnishing R-enantiomerafter hydrolysis
• Non-preferred Re-face additionfurnishing S-enantiomerafter hydrolysis
Diastereofacial Selection
Cl
Me2N
Cl
Cl
Cl
NC Cl
91 %
94 %
Cl
OCl
O
PhCl
O
HCl
Aryl-Cl eeEntry
4 100 °C 11 h 94 %
5 100 °C 12 h
2 100 °C 18 h
1
3
59 %
60 %
91 %57 %
100 °C 9 h 68 %
6
7
100 °C 20 h 90 %55 %
100 °C 8 h 93 %69 %
100 °C 8 h 92 %67 %
100 °C 8 h 96 %60 %
100 °C 8 h 92 %65 %
8
9
Isolated YieldTemp. Time
OCl
O
HCl
Aryl-Cl eeEntry
1
140 °C 1 h
2
85 %62 %3
140 °C 1 h 89 %63 %4
Isolated YieldTemp. Time
Classical heating Microwave heating
Cl
Cl 140 °C 1 h 88 %54 %
140 °C 1.5 h 84 %50 %
Gopal et al. Submitted
O
Ar
Asymmetric Chelation-Assisted Heck Arylation with Aryl Chlorides
(R)-2-Aryl-2-methyl-cyclopentanones
0
10
20
30
40
50
60
70
80
90
100
0 4 8 12 16
∆∆∆∆∆∆∆∆G‡ (kJ/mol)
ee (%
)
0 degrees C
100 degrees C
200 degrees C
Requirements for High Selectivity
• Enantiomeric excess as a function of the difference in activation energy (∆∆(∆∆(∆∆(∆∆G‡) for an enantioselectiveprocess at different reaction temperatures
Larhed et al. Acc. Chem. Res. 2002, 717; Bremberg et al. Synthesis 2000, 1004
6
Microwave-Accelerated Heck Spiro-Cyclizations of o-Halobenzyl
Cyclohexenyl Ethers
• Spiro[cyclohexane-1,1’-isobenzofuran] compounds• New constrained products by 5 -exo cyclization
O
XR1 R2
R1 R2OMicrowaves
[Pd]
Regioselectiveproducts
X = I, Br
Svennebring et al.
Cyclization Precursors
• Eight starting materials in good yields
HO
X
OOH
OHO
X
PTSA
Ac 2O Et3N
X = Br 92%X = I 87%
DMAP
OO
X
X = Br 83%X = I 77%
OAcO
X
X = Br 90%X = I 89%
NaBH4+
Distd MeOH /dioxane1:1
O
PTSA
HO
Xbenzene
O
X
O
XO
X = Br 85%X = I 77%
+
+MW220 °C5 minDMAc
Svennebring et al. J. Org. Chem. 2007, 5851
Heck Spiro-Cyclizations
Temp(°C)Starting material
OO
X
O
X
OHO
X
PdOAc 2
OAcO
I
I DMF
DMF
OO
O
OAcO
OO
BrBrII
Br
II
Br
II
ConditionsHeating
Solvent(%) Time
1%1%1%1%
TolueneToluene
Toluene/H 2O 19:1Toluene/H 2O 19:1
Microwave
MicrowaveClassical
Classical
180120140100
10 min18 h10 min18 h
82%71%91%82%
1%1%1%
Toluene
Toluene/H 2O 19:1Toluene/H 2O 19:1
Microwave
ClassicalMicrowave
180140100
10 min10 min18 h
51%59%58%
1% Microwave 140 10 min 54%
10%1%10%
Toluene/H 2O 19:1DMF/H2O 19:1
Microwave
MicrowaveMicrowave
180140140
10 min4 h10 min
63%54%77%
Yield Product
Svennebring et al. J. Org. Chem. 2007, 5851
HIV/AIDS Statistics 2006
• 40 million people lll infected
• 4.3 million newly infected
• 2.9 million deaths in AIDS
• 1930±±±±15 years lll transmission of SIV to lll humans
• Early 1980s AIDS
• 1983 isolation of HIV
• 1987 first antiretroviral lll therapy
• 1995 first protease lll inhibitor
Target: HIV-1 Protease
Microwave-assisted synthesis of protease inhibitors :Alterman et al. J. Med. Chem. 1999, 3835; Schaal et al. J. Med. Chem. 2001, 155;Nöteberg et al. J. Med. Chem. 2003, 734; Nöteberg et al. J. Comb. Chem. 2003, 456;Ersmark et al. J. Med. Chem. 2004, 110; Ax et al. Bioorg. Med. Chem. 2005, 755;Muthas et al. Bioorg. Med. Chem. 2005, 5371; Wannberg et al. J. Comb. Chem. 2005, 611;Ersmark et al. J. Med. Chem. 2005, 6090; Gold et al. Tetrahedron , 2006, 4671; Ekegren et al. J. Med. Chem. 2006, 1828; Wannberg et al. Bioorg. Med. Chem. 2006, 5303Reviews: Ersmark et al. Cur. Opin. Drug Discov. Dev. , 2004, 417; Wannberg et al Top. Curr. Chem. 2006. 266, 167
HIV-proteaseC2 symmetric dimer
Concerns:1) Active mutants 2) Metabolic stability3) Improved cell permeability
Brik et al. Org. Biomol. Chem. 2003, 5
HIV-1 Protease
• HIV-1 protease is an aspartic protease
• Transition-state mimics inhibit the enzyme
OH
HOO H OO
O
NH
NH
OOHOO
NNH O O
H
H
H
OO H OO
O
OHNH
NH2
(-)
P1
P1'
(-)
P1
P1'
(-)
P1
P1'
Asp 25 Asp 25' Asp 25 Asp 25' Asp 25 Asp 25'
NH
OH
O
P
P OH
NH
OH
NH
P
O
P
NH
OH
NH
O
P
P
Dihydroxyethylen Hydroxyethylamin
1
1'
1 1'
tert -Hydroxyethylamin
1'
1
7
A New HIV-1 Protease Inhibitor C1 Core Structure
• Aim
Ekegren, J. K. Et al. J. Med. Chem . 2005, 8098
A tertiary alcohol in the transition-state mimickin g scaffold
New
NNH
OH
O
OH N
HN O
O NH
HN N
NH
O
O
OOH
N
HN O
O
N
AtazanavirK i = 2.66 nMEC50 = 0.0039 µµµµM
IndinavirK i = 0.52 nMEC50 = 0.041 µµµµM
NH
OH
O
OHN
NH
HN
R'
O
R
R''
P1
P2 P1'
P3'
P2'
A New HIV-1 Protease Inhibitor C1 Core Structure
HO
HN
R
O HN
NH
HN
R
Br O
54-76%
OH
NH
O
NNH
O HN
R
Br
46-59%
Ti(Oi-Pr)4, THF, 40 °C
HN
NH2
Br
+
EDC, NMM HOBT
EtOAc, rt
OH
OHNH
OO
(S)-isomer
Ekegren et al. Org. Biomol. Chem. 2006, 3040Wu et al. Organometallics 2006, 1434
• Shielded tertiary nalcohol by epoxidenopening l
Evaluation of the New Tertiary Alcohol C1 Transition-State Mimic
Biological results Binding mode
K i = 2.4 nM
EC50 = 1.1 µM – how to improve?
O
NH
OHOH
NNH
HN
O
Br
O
O
Br
S
CO2Me
t-Bu
Papp = 42 x 10-6 cm/s
Cl int = 266 mL/min/mg Ekegren, J. K. Et al. J. Med. Chem . 2005, 8098
Asp25 binds to backbone N instead of OH
P1′′′′ Decorations by Microwave Pd(0)-Catalyzed Cross-Coupling Reactions
• Enzyme inhibition and in vitro anti-HIV activity
• Improved Caco-2 and intrinsic clearance data
OHNH
O
NNH
HN O
O
OOH
Br
N
N
O
O
ON
4-Br 3-Br
N
N
N
N
N
S
OHNH
O
NNH
HN O
O
OOH
R''
4-R'' 3-R''
[Pd], MW
R'' =
* * * *
* only in the para series
20 - 60 min17 - 62%
OHNH
O
NNH
HN O
O
OOH
N
Ki = 5 nMEC50 = 0.18 µµµµM
Para compounds: EC50 = 0.18-1.1 µµµµM
Meta compounds: Only 2 of 9 active in cell assay
3- and 4-pyridyl in para EC50 = 0.18-0.22 µµµµM
Papp = 33 x 10 -6 cm/s
Cl int = 154 µµµµL/min/mg
Ekegren, J. K. Et al. J. Med. Chem . 2006, 1828
A New Elongated Tertiary Alcohol HIV Protease Inhibitor?
Wu, X. and Öhrngren, P. et al. J. Med. Chem . In revision
O
HN N
NH
O
O
OOH
N
HN O
O
Atazanavir8-atom spacer
NH
OH
O
OHN
NH
HN
O
R''
C1 tert- OH inhibitor6-atom spacer
O
O
NH
OH
O
OH
C3 tert- OH inhibitor8-atom spacer
NNH
HN
O
R''
O
O
• Water coordination optimized• New synthetic route needed
New C3 target scaffold
A New Elongated HIV-1 Protease Inhibitor C3 Core Structure
TBSO
NH
O
OTBSOH
HN
NH
HN
Br OO
O
TBSO
NH
O
OTBSN
NH
O HN
Br
O
O
OH
NH
O
OHN
NH
O HN
R
O
O
48%
1. Dess-Martin, 2. Na(OAc) 3BH
1. [Pd], RMR'n, MW
20 min, 120 or 130 oC
2. TBAF
14 Examples67% average yield
• P1’ optimization by lllSuzuki and Stille lll couplings
Wu, X. and Öhrngren, P. et al. J. Med. Chem . In revision
8
Antiviral Activity and X-Ray Binding Mode
12d
OH
NH
O
OHN
NH
OR
HN O
O
• Improved water binding lll but tert -OH binds only lll to one aspartate residue
R-group K i nM
EC50
µµµµM CC50 (µµµµM)
Ph 5.7 1.20 >10 4-F-Ph 6.7 0.98 >10 4-Cl-Ph 3.4 0.91 >10 4-Br-Ph 3.3 0.85 >10 4-CN-Ph 2.9 1.20 >10 4-NMe2-Ph 4.9 0.98 >10 CH(CH3)2 6.8 1.80 >10
N 2.8 0.47 >10
N
N
2.4 0.22 >10 ON 3.6 0.50 >10
N
O 11 0.88 >10
N N
3.3 0.17 >10 N
O
N 3.6 0.19 >10
N
S 2.3 0.21 >10 N
S 3.5 0.51 >10 N
S 24 1.00 >10
N
N
S 2.3 0.48 >10
O S
N
Cl 5.5 0.60 >10
4-I-Ph 4.5 0.82 >10
7.3 0.78 7.5
N 3.6 0.19 >10 N 2.8 0.17 >10
S 10 0.56 >10
Acknowledgement
– Prof. Anders Hallberg
– Prof. Bertil Samuelsson
– Prof. Åke Pilotti
– Prof. Anders Karlén
– Prof. Torsten Unge
– Prof. Kristina Moberg
– Dr. Per Sjöberg
– Dr. Anja Sandström
– Dr. Xiongyu Wu
– Dr. Murugaiah Andappan
– Dr. Peter Nilsson
– Dr. Luke Odell
– Dr Ulf Bremberg
– Dr. Prasad Appakuttan
– Dr Robert Rönn
– Dr. Jenny Ekegren
– Dr. Stefanie Schlummer
– Dr. Johan Wannberg
– Dr. Andreas Svennebring
– Dr. Per-Anders Enquist
– Gopal Datta
– Per Öhrngren
– Jonas Lindh
Acknowledgement
• Swedish Foundation for Strategic Research• The Swedish Research Council• Knut och Alice Wallenbergs Foundation• Medivir AB
Division of Organic Pharmaceutical Chemistryat Uppsala University
Reactive Intermediates
UniqueIsotopicPattern
CationicPathway
On-LineMonitoring
ESI-MS
Pd
m/z112110108106104102100
norm
alis
ed in
tens
ity
Mechanistic Investigation of the Oxidative Heck Reaction
O2
H 2O2
C σσσσ
Pd(II)N
N
Pd(II)N
Ar N
Pd(II)N
Ar N
R
R
ArPd(II)
N
NR
Ar Pd(II)H
N
NR
Ar
Ar B(OH )2
D
E
RB
III
II
I
IV
V
VIA
C ππππ
Pd(II)H N
N
O2
H 2O2
C σσσσ
Pd(II)
N
N
Pd(II)
N
Ar N
Pd(II)
N
Ar N
R
R
ArPd(II)
N
NR
Ar Pd(II)H
N
NR
Ar
Ar B(OH )2
D
E
RB
III
II
I
IV
V
VIA
C ππππ
Pd(II)H N
N
N N
Electrospray Ionization Mass Spectrometry ESI-MS
• A mass spectrometer needs the sample to be gaseous. The ESI technique solves this problem without heat.
9
MS Spectrum ( m/z = 100-800)
MS spectrum for the standard reaction
100 200 300 400 500 600 700 800
m/z
Inte
nsity
A3
A2
A1
B1
B2
C1F1
B3
2a+Na+
2a+MeCN+Na+
4a+Na+
2[4a]+Na+
3[4a]+Na+
4a+2a+Na+
4a+MeCN+Na+
2MeCN+Na+
Pd OAcN
N
NN
N
N
Pd OAc
Pd OAcN
N
N
N
N
N
Pd
PdN
N
N
entry m/z-ratio Pd(II)-complex
A1
A2
A3
B1
B2
373
455
581
405
446
1
2
3
4
5
Structural Proposition of Observed Complexes
N
OPd
N
N
PdN
N
NN
NO
Pd
N
N
PdN
NNH
or C1
D1
B3613
516
538
6
7
8
entry m/z-ratio Pd(II)-complex
Single Charged Cationic Palladium(II) Complexes Detected in the Standard Oxidative Heck Reaction with Using ESI-MS-(+) AnalysisEnquist et al. J. Org. Chem. 2006, 8779
MS Spectrum ( m/z 440-454)
MS spectrum of Pd complex B2 (C23H22N3Pd, m/z 446) solid line, and theoretical isotopic pattern dotted line
B2
0
20
40
60
80
100
440 442 444 446 448 450 452 454
m/z
Nor
mal
ized
Inte
nsity
(%
)
B2
0
20
40
60
80
100
440 442 444 446 448 450 452 454
m/z
Nor
mal
ized
Inte
nsity
(%
)
PdN
N
N
B2
• MS-MS spectrum of Pd complex B2 ( m/z 446)
MS-MS (Tandem Mass)
0 50 100 150 200 250 300 350 400 450
m/z
Inte
nsi
ty
B2405
313
224
207
PdN
N
N
B2m/z 446
- MeCN- Pd
- Toluene
Chemical Verification and Conclusion
R
B(OH)2
N
OPd(OAc) 2, ligand
R=MeR=n -Bu
N N N N
Ph Ph
N
O
R
+NaOAc, solvent air, rt
( )nn=1n=3
( )n
Solvent: MeCN or EtCN Ligand:
• Exchange of reaction components to chemically equivalent componentswith different mass provides the expected m/z ratios
• In conclusion– Three different types of observed palladium interme diates:
(A) Starting intermediates, (B) Transmetallation int ermediates, (C) Insertion intermediate
• The suggested catalytic cycle seems to be correctEnquist et al. J. Org. Chem. 2006, 8779
