(+)-Ingenol from

14-Step Synthesis of (+)-Ingenol from (+)-3-Carene
Lars Jørgensen, Steven J. McKerrall, Christian A. Kuttruff, Felix Ungeheuer,
Jakob Felding, Phil S. Baran, Science, Published online 1 August 2013, DOI: 10.1126/science.1241606
“…I think that most organic chemists had considered ingenol beyond the reach of scalable chemical synthesis…” P. S. Baran Me
Me
Me
(+)-3-Carene
Me
TMSO
Me
Me
O
H
OTBS
Me
Me
O
Me
Me
Me
H
HO HO
HO
OH
(+)-Ingenole
Raffaele Colombo – 8/24/2013 Raffaele Colombo @ Wipf Group
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Ingenol Ingenol is a diterpenoid first isolated by Hecker in 1968 from Euphorbia ingens The structure was elucidated through X-­‐ray crystallography by Hecker in 1970 and contains a unique bicyclo[4.4.1]undecan-­‐11-­‐one core (rings BC) whit a in,out intrabridgehead rela=onship Ingenol esters showed: -­‐ an.cancer ac.vity in vivo -­‐ an. HIV ac.vity in vitro Ingenol mebutate (Picato®, Leo Pharma) is FDA approved (2012) for the treatment of ac=nic keratosi and has completed phase II clinical trials for the topical treatment of basal cell carcinomas Raffaele Colombo @ Wipf Group
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Me
Me
O D
Me
Me
O
C
A
H
B
HO HO
HO
H
OH
C
H
B
in-out-[4.4.1]-undecane
(+)-Ingenole
Me
Me
O
Me
Me
H
O
O HO
HO
OH
Picato®
8/24/2013
Ingenol mebutate The current sources of ingenol mebutate are: -­‐  direct isola=on from E. peplus (commercial source) -­‐  semisinthesis from ingenol Isola=on of ingenol mebutate and ingenol are: 1.1 mg of ingenol mebutate per Kg of E. peplus 275 mg of ingenol per Kg of E. lathryis Me
Me
O
Me
Me
Me
Me
protection
H
HO HO
HO
Acetone, PTSA
OH
Me
Me
Me
O
Me
H
angeloylation
LiHMDS
HO HO
O
O
O
O
O
ingenol
Me
Me
Me
O
Me
H
O
deprotection
H3PO4
O HO
O
O
Me
Me
O
H
O
O HO
HO
OH
on 6 g scale:
31% over 3 steps
3 crystallyzation
ingenol mebutate
SynleK 2012, 23, 2647-­‐2652 (Leo Pharma procedure) Raffaele Colombo @ Wipf Group
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Ingenol -­‐ previous approaches 3 total synthesis: -­‐  Winkler (2002): [2+2] photocycloaddi=on – 43 steps, 0.007% -­‐ racemic -­‐  Tanino/Kuwajima (2003): pinacol rearrangement – 45 steps, 0.03% -­‐ racemic -­‐  Wood (2004): ring close metathesis -­‐ 37 steps, 0.002% -­‐ asymmetric 1 formal synthesis: -­‐ Kigoshi (2004): ring close metathesis – 36 steps, 0.01% based on Winkler’s route, asymmetric Me
Me
11
A
OC
D
Me
Me
H
B
HO HO
HO
Synthethic challenges: -­‐  in-­‐out intrabridgehead stereochemistry -­‐  4 hydroxyl groups int the south part -­‐  Sterochemistry at C-­‐11 OH
(+)-Ingenol
Raffaele Colombo @ Wipf Group
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Winkler’s strategy CO2Me
O
OTBS
1) Li/NH3
methyl crotonate
O
O
vs
H
Cl
Cl
OMe
O
60%
O
O
O
Cl
hv
CH3CN
H
K2CO3
O-
H
1) SeO2, TBHP
2) (Cl3C)2CO
Cl
H
O
3 steps
H
O
H
H
4 steps
H
14:1 d.r.
O Li
O
Li
O
O
2) TBSOTf
O
O
O
O
O
[2 + 2]
O
H
H
H
H
O
O
60%
retro-aldol
Cl
O
Me
H
H
O
H
Cl
H
OMe
O
H
CO2Me
O
Me
6 steps
Me
H
H
27 steps
OTBS
Me
HO HO
HO
O
Me
Me
H
OH
Winkler, J. D.; Rouse, M. B.; Greaney, M. F.; Harrison, S. J.; Jeon, Y. T. J. Am. Chem. Soc.. 2002, 124, 9726-­‐9728. Raffaele Colombo @ Wipf Group
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Tanino/Kuwajima’s strategy AcO
OH
Br
O
6 steps
OMe
OMe
OH
3 steps
COOtBu
OTES
OMe
OMe
Co(CO)3
Co(CO)3
OH
6 steps
OTIPS
OTIPS
OMe
Ar =
MeAl(OAr)2
NO2
CH2Cl2
pinacol rearrangement
Me3Al
CH2Cl2
O
HO
H
Co(CO)3
O
HO
TBHP
H
HO
1) Li/NH3
H
Ti(OiPr)4
OMe
OTIPS
OMe
OTIPS
OMe
OTIPS
Co(CO)3
OH
2) CHBr3, NaOH
3) Me3CuLi2, MeI
OMe
N
HO
O
1) N N
O
7 steps
MeO
OTIPS
H
2) NaBH4
3) TES-Cl
O
Me
13 steps
H
H
MeO
O
O
Me
HO HO
HO
O
OTIPS
Me
Me
H
OH
Tanino, K.; Onuki, K.; Asano, K.; Miyashita, M.; Nakamura, T.; Takahashi, Y.; Kuwajima, I. J. Am. Chem. Soc.. 2003, 125, 1498-­‐1500. Raffaele Colombo @ Wipf Group
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Wood’s strategy CH2=CH2
(PCy3)2Cl2RuCHPh
O
4 steps
O
PhH, !
BF3.Et2O
O
O
10 steps
O
O
ring-opening metathesis
OPMB
98%
Mes N
ring-closing
metathesis
76%
N Mes
Cl
Cl
O
O
O
1) DMP
H
H
2) RhCl3
O
H
HO
O
SeO2
4 steps
H
tBuOOH
H
H
O
H
OPMB
O
O
H
OPMB
OPMB
OPMB
tBuOK,
O2, P(OMe)3
O
O
4 steps
H
H
OPMB
O
H
DBU
H
86%
O O
O HO
O
4 steps
O
O O
OPMB
O
SO2Me
O
1) Na(Hg)
2) HCl
H
3) SeO2
O O
HO
SO2Me
28%
HO HO
HO
OH
(+)-Ingenol
Total Synthesis of Ingenol. Nickel, A.; Maruyama, T.; Tang, H.; Murphy, P. D.;. Greene, B.; Yusuff, N.; Wood, J. L.. J. Am. Chem. Soc. 2004, 126, 16300-­‐16301 Raffaele Colombo @ Wipf Group
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Kigoshi’s strategy (formal synthesis) I
THPO
NaH
MeO2C
O
1) LiI
2) PPTS
MeO2C
O
75%
1) Ph3P, CCl4
2) Et3CONa
O
76%
50%
O
Funk's keto ester
THPO
THPO
1) LDA
59%
Mes N
2)
Br
N Mes
Cl
Cl
O
H
H
O
O
SeO2
H
85%
H
CHO
87%
O
Winkler's aldehyde
Watanabe K, Suzuki Y, Aoki K, Sakakura A, Suenaga K, Kigoshi H. J. Org. Chem. 2004, 69, 7802-­‐7808 Raffaele Colombo @ Wipf Group
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This work Highly stereocontrolled synthesis of (+)-­‐ingenole star.ng from (+)-­‐carene ($10.2/mol) 14 steps 1.2% overall yield 2 phases strategies: cyclase and oxidase Me
Me
Me
(+)-3-Carene
cyclase phase
7 C-C bonds
5 stereocenters
Me
HO
7 steps
Me
TMSO
Me
Me
H
OTBS
Me
(1.08 g)
rearrangement/
oxydase phase
4 C-O bonds
4 stereocenters
7 steps
Me
O
Me
Me
Me
H
HO HO
HO
OH
(+)-Ingenole
Raffaele Colombo @ Wipf Group
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This work Highly stereocontrolled synthesis of (+)-­‐ingenole star.ng from (+)-­‐carene ($10.2/mol) 14 steps -­‐ 1.2% overall yield 2 phase strategy: cyclase and oxidase Me
cyclase
phase
(+)-3-Carene
ZnMe2
cyclase phase
7 C-C bonds
5 stereocenters
7 steps
Me
TMSO
Me
Me
H
OTBS
Me
H
H O
O
O
Me
Me
HO
Me3Al
Br
Me
Me
(1.08 g)
(+)-"taxadienone"
8 steps, 18-20% overall yield
rearrangement/
oxydase phase
4 C-O bonds
4 stereocenters
7 steps
oxidase phase
AcO
O OH
Me
Bz
Me
NH O
O
Ph
OH
O
O
H
OH O OAc
O
Taxol Ph
Me
Me
H
HO HO
HO
OH
(+)-Ingenole
A. Mendoza, Y. Ishihara, P. S. Baran. Nature Chemistry 2012, 4, 21–25 Raffaele Colombo @ Wipf Group
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Biosynthe.c inspira.on O
O
P
P
O - O - OO
O
2
Cyclase phase OPP
OPP
H
H
H
H
OPP
H
H
geranylgeranyl
pyorophosphate
Rearrangement/ oxidase phase OH
casbene
(31 mg/L engineered
in S. cerevisiae)
lathyrane type
O
O
H
H
tigliane type
O
H
H
O
H
H
[putative byosinthetyc intermedie]
OH
HO HO
HO
ingenane type
Ingenol
OH
O HO
HO
OH
Ingenol mebutate
(31 mg/Kg in E. peplus)
OH
H
OH
H
O HO
OH
phorbol
[tigliane type]
1 total synthesis (36 steps)
Raffaele Colombo @ Wipf Group
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Cyclase phase OH
Me
16
Me
Me
Me
NCS, DMAP
Cl
DCM, rt
O3, DCM/MeOH, -78 °C
then thiourea, -78 °C to rt
1
2
Me
Me
Me
O
Me
Me
H
Br-Mg
, THF
OH
H
HO
-78 °C to -15 °C
Me
Me
Me
TBSOTf, Et3N,
DCM, 0 °C,
then TMSOTf, Et3N
OH
Me
81%
4
71%
5
Me
TMSO
Me
Me
O
H
OTBS
Me
7
Raffaele Colombo @ Wipf Group
MeMgBr, THF
-78 °C to 0 °C
O
Me
17
65 °C (or 80 °C)
Cl
Me
Me
O
3
48% over 2 steps
Me
IBX (2 eq), THF,
LiNap, THF, -78 °C,
then HMPA, MeI, -78 °C to rt
then LiHMDS, 17
44%
Me
Me
Me
H
TMSO
[RhCl(CO)2]2, CO
p-xylene, 140 °C
OTBS
Me
72%
6
Me
TMSO
Me
Me
Me
HO
H
OTBS
Me
80%
8
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Rearrangement/oxidase phase Me
TMSO
Me
Me
Me
HO
Me
TMSO
Me
OsO4, Py, rt
H
OTBS
then Na2SO3, THF
HO
H
OTBS
HO
HO
Me
Me
8
BF3.Et2O, DCM
-78 °C to -40°C
H
OTBS
O
64% over 2 steps
O
O
O
Me
Me
Me
Me
H
OH
Martin's sulfurane
CHCl3, reflux
Me
H
AcO O
50°C
OTBS
O
Me
90%
SeO2, HCOOH,
dioxane, 80°C
Me
Me
O
Me
Me
H
then NaOH
HO HO
HO
81%
HF, CH3CN,
H
12
then NaOH, THF
Me
13
O
Me
Me
O
Me
Me
Me
Me
O
59%
11
O
O
then Ac2O, Py, DMAP
OTBS
O
Me
10
SeO2, dioxane, 80°C
H
Me
Me
HO
DCM, rt
Me
Me
O
80%
O
CDI, DMAP
Me
Me
O
Me
then MeOH/Et3N
-40 °C to rt
AcO O
Me
Me TMSO
9
Pinacol rearrangement
Me
Me
Me
HO HO
HO
Me
14
76%
OH
Ingenole
Martinʼs sulfurane#
Raffaele Colombo @ Wipf Group
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Key step 1 Me
O TMSO
Pauson - Khand [2 + 2 + 1]
Me
Me
Me
TMSO
H
LnRh
LnRh
Me
TMSO
Me
Me
LnRh
or
Me
Me
Me
O
H
OTBS
-LnRh
Me
Me
Me
H
OTBS
O
6
Me
TMSO
Me
Me
TMSO
LnRh
OTBS
OTBS
H
OTBS
CO
H
Me
Me
Me
7
Me
R1
5 mol%[Rh(CO)2Cl2]
R1
R4
R3
R2
n = 1, 2
n
CO(1 atm), toluene
O
R4
O
60%
C6H13
COOEt
C6H13
n
R3
iPr
R2
iPr
K. M. Brummond, H. Chen, K. D. Fisher, A. D. Kerekes, B. Rickards, P. C. Sill, S. J. Geib. Organic LeKers, 2002, 4, 1931-­‐1934 Raffaele Colombo @ Wipf Group
COOEt
COOEt
COOEt
COOEt
COOEt
O
COOEt
COOEt
76%
Ph
Ph
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COOEt
COOEt
O
77%
COOEt
COOEt
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Key step 2 Pinacol-type rearrangement
O
Me
HO
O
Me
10
Raffaele Colombo @ Wipf Group
Me
Me
H
OTBS
O
O
Me
Me
TMS
Me
BF3.Et2O, DCM
-78 °C to -40°C
Me
then MeOH/Et3N
-40 °C to rt
80%
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O
Me
H
OTBS
O
O
O
Me
11
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Key step 2 Pinacol-type rearrangement
Me
Me
O
Me
HO
H
OTBS
O
O
Me
Me
TMS
Me
O
Me
BF3.Et2O, DCM
-78 °C to -40°C
Me
then MeOH/Et3N
-40 °C to rt
H
OTBS
O
O
O
80%
10
O
Me
Me
11
“Bio” vs “chem” inspira.on H+
OH
OH
Me
H
H
H
Me
OH
OH
H
MeOH
O HO
OH
[putative biosinthetyc intermedie]
O
Me
Me
Me
MeOH
H
H+
HO HO
HO
Ingenol
OH
Me
Me
Me
49%
HO
HO
HO HO
HO
H
OH
tigliane - type
phorbol
G. Appendino, G. C. Tron, G. Cravolo, G. Palmisano, R. Annunziata, G. Baj, N. Surico, European Journal of Organic Chemistry, 1999, 12, 3413–3420 Raffaele Colombo @ Wipf Group
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SeO2 oxida.ons Baran O
O
O
O
O
H
SeO2, dioxane, 80°C
OTBS
then Ac2O, Py, DMAP
Me
O
H
AcO O
59%
O
H
OTBS
O
O
SeO2, HCOOH,
dioxane, 80°C
H
then NaOH
HO HO
HO
76%
HO HO
HO
OH
Ingenol
(Shibuya’s condi=on) Shibuya, K., Synth. Commun., 1994, 24, 2923-­‐2941 O
O
H
SeO2
O
O
SeO2
H
H
H
tBuOOH
H
OPMB
49%
HO
HO HO
HO
H
OPMB
40%
Me
HO HO
HO
OH
Ingenol
Wood Raffaele Colombo @ Wipf Group
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“Hidden” steps OH
Me
OH
OEt
OEt
OEt
O
!
!
O
O
LiAlH4
O
O
O
-EtOH
OEt
65%
(over 2 steps)
Pseudomona cepacia
OH
OH
vinyl acetate
racemic
enzymatic
resolution
Me
26%
98.7% e.e.
3 more steps, 17% overall yield
Raffaele Colombo @ Wipf Group
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Wipf Group Raffaele Colombo @ Wipf Group
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Key step procedures Pauson Khand A 1L three-­‐neck flask was charged with a soluUon of 6 (1.5 g, 3.25 mmol, 1.0 equiv) in anhydrous p-­‐xylene (650 mL) and the soluUon was degassed using carbon monoxide under sonicaUon. [RhCl(CO)2]2 (126.3 mg, 0.325 mmol, 0.1 equiv) was added and the reacUon mixture was transferred into a preheated oil bath and sUrred at 140 °C under 1 atm of CO for 12 h. Pinacol rearrangement To a soluUon of 10 (191 mg, 0.338 mmol, 1.0 equiv) in DCM (7 mL) was added BF3.Et2O (420 μL, 3.38 mmol, 10 equiv) dropwise at -­‐78 °C. The reacUon mixture was sUrred at this temperature for 2 min before being warmed to -­‐50 °C. Acer 30 min, a 1:1 mixture of Et3N/MeOH (3 mL) was added at -­‐40 °C, the soluUon was sUrred for 2 min and saturated aqueous NaHCO3 (5 mL) was added… Raffaele Colombo @ Wipf Group
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Winkler: first steps Raffaele Colombo @ Wipf Group
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Winkler: last steps Raffaele Colombo @ Wipf Group
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Winkler: final steps Raffaele Colombo @ Wipf Group
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Tanino: first steps Raffaele Colombo @ Wipf Group
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Tanino: final steps [1] Trost, B. M.; Preckel, M. J. Am. Chem. Soc. 1973, 95, 7862-­‐7864 Raffaele Colombo @ Wipf Group
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Tanino: final steps Raffaele Colombo @ Wipf Group
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Wood: first steps Raffaele Colombo @ Wipf Group
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Wood: final steps Raffaele Colombo @ Wipf Group
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