Topic Seminar PPT.Pptx

A Second Generation Total Synthesis of (±)-Cycloclavine and Progress Toward an Asymmetric Total Synthesis of (+)-Cycloclavine

N H

Steph McCabe Research Topic Seminar 30th January 2016

Steph McCabe @ Wipf Group Page 1 of 25 3/27/2016 Overview

PART 1: 1.1 Ergot alkaloids § Classification § Natural sources/ history § Biological activity and use as pharmaceuticals

1.2 Clavine Alkaloids § Classification/ examples § Biosynthesis of clavine alkaloids § Summary of recent syntheses of clavine alkaloids based on strategic disconnections • Clavicipitic acid • Aurantioclavine • Rugulovasine A & B • Cycloclavine § Recent syntheses of cycloclavine

PART 2: Experimental Data § Retrosynthetic analysis § Second generation total synthesis of cycloclavine § Efforts toward an asymmetric synthesis of cycloclavine § Future directions § Conclusions

Steph McCabe @ Wipf Group Page 2 of 25 3/27/2016 Classification of Ergot Alkaloids

ERGOT ALKALOIDS

Clavines Lysergic Acid 8 NH D R = H or OH R H HO C 8 8 C 2 NH NH D H D H A B 2 C H C N H H 1 A B 2 A B 2 Ergoline Core N 1 N 1 H H lysergic acid tetracyclic clavines R O (ergolines) O N R = H, CH2OH, CHO R NRR' R N O NH HN N OH H H O N H O N H H H

NH NH NH NH tricyclic clavines Rearranged clavines Lysergic acid amides ergopeptines (secoergolines)

Steph McCabe @ Wipf Group Page 3 of 25 3/27/2016 Ergot Alkaloids Occurrence of Ergot Alkaloids in Nature

§ Ergot alkaloids are produced by the Clavicipitaceae and Trichocomaceae families of filamentous fungi

§ These fungi infect cereal grains causing ‘ergot’

§ The fungi have a symbiotic relationship with the plant causing no symptoms of infection • Ergot alkaloids produced by the fungi help protect the plant from predation and improve growth, while the fungi gain nutrition and shelter from the plant

Ergot on wheat stalks fruiting C. purpurea sclerotia

Nat. Prod. Rep., 2011, 28, 496 Nat. Prod. Rep., 2014, 31, 1328

Steph McCabe @ Wipf Group Page 4 of 25 3/27/2016 History Ergot & Ergotism

§ Consumption of ergot contaminated grains leads to ergotism (St. Anthony’s fire), a disease common in central Europe in the middle ages

§ Two types of ergotism are recognized: • ergotismus convulsivus: characterized by hallucinations, convulsions, confusion and irrational behaviour • ergotismus gangrenous: characterized by gangrene of the feet, legs, hands and arms

§ Ergotism in humans is now rare due to strict guidelines governing the acceptable concentration of ergot bodies in grain, however ergotism still produces serious epidemics in livestock fed contaminated grain.

§ Modern control of ergot is focused on limiting the presence of sclerotia in cereal grains largely through preventative measures or in particularly bad seasons crops can be saved by separating the ergot kernels from cereal grains based on density or colour

Steph McCabe @ Wipf Group Page 5 of 25 3/27/2016 828 A. M. Beekman and R. A. Barrow Biological Activity of Ergot Alkaloids Owing to the concurrent development of many of the drugs the pharmaceutical classes. Within each class, the name of discussed, and the spectrum of activity some pharmaceuticals the fungal metabolite is presented as well as the pharmaceutical Bu

iPr HO OH H O O iPr N N O HO display, this review is presented in fungal metabolite classes companies thatN supply it and brand names that it is sold under. N HO O R2N H 6 O NH OH NH O O NH H H OMe O OMe N N O O H R N H H COOH O O rather than chronologicallyHO or by pharmacology.S To provideR N S ForH thoseiBu classes that haveO HN OH several members, a time-line O HO O O O N O O OH O O N O N HO NH 7 MeO O MeO O O O R OH COOH O 1 iPr O H N Cl O HO NH H O NH O iBu N context, Fig. 1 displays a timeline of the original discoveryO ofOH displayingO approval dates is presented forNH clarity. Table 1 HO N N OH 2 H N O OH O iBu O HO

MycophenolicErgot acid alkaloidsPenicillins Griseofulvin Coumarins CephalosporinsFusidic acidCyclosporin EchinocandinsStatins Fingolimod

1896 1918 1928 1939 1941 1948 1962 1971 1974 1976 1995 Figure 1. Timeline of the initial discovery of pharmaceutical classes of fungal metabolites Fig. 1. Timeline of the original discovery of the pharmaceutical classes of fungal metabolites.

§ These classes of fungal metabolites have produced some of the best known/ profitable pharmaceuticals in human Table 1. Pharmaceuticals currentlymedicine available in Australia and New Zealand, displaying drug name, structure, pharmaceutical class (underlined), original fungus (italicised),• Anti-cholesterol nature statins of discovery, e.g. rosuvastatin and earliest (crestor), year atorvastatin of approval (lipitor), inantibiotic Australia penicillin[11] and New Zealand[12] and immunosuppressant cyclosporin A § Ergot alkaloids possess the widest spectrum of biological activity Cephalothin • Ranging from anti-migraineCephalexin to anti-Parkinson agents Cephazolin Cefuroxime axetil N N N O Aus. J. Chem., 2014, 67, 827 N N NH2 O H H O N H H O HN6 H S N S S S HN H O Steph McCabe @ Wipf Group O Page 6 of 25 S N 3/27/2016 N O N O O O N O O O OOH O O O OOH S S NH O OH O 2 N N O Cephalosporins Cephalosporins Cephalosporins Cephalosporins Cephalosporium acremonium Cephalosporium acremonium Cephalosporium acremonium Cephalosporium acremonium Semi-synthetic Semi-synthetic Semi-synthetic Semi-synthetic 1988 1969 1974 1989 Cefaclor Cefotaxime Ceftriaxone Ceftazidime

H2N S H2N H2N N S NH2 S N H N N H O N S O H H HN S N O O N N H N S O H O N HN S O Cl O N O O O ϩ O S N OH N N OOH NH O O OH O O OH N Ϫ O O O O Cephalosporins Cephalosporins Cephalosporins Cephalosporins Cephalosporium acremonium Cephalosporium acremonium Cephalosporium acremonium Cephalosporium acremonium Semi-synthetic Semi-synthetic Semi-synthetic Semi-synthetic 1980 1981 1983 1984 Cefepime Warfarin Cyclosporin Caspofungin

OH H2N OH OH S H N N HN HO O HO NH2 O O O O O N H OH O NH N O HO N H N N N O O N S N O HN O O HN OH O NH NH N N ϩ N O H N O OH O O N N O O O N OH NH2 H HN Ϫ O O O O O Cephalosporins Coumarins Cyclosporin Echinocandins Cephalosporium acremonium Penicillium sp. Tolypocladium inflatum Zalerion arboricola Semi-synthetic Designed Natural Semi-synthetic 1997 1954 1983 2002 (Continued) Biological Activity of Ergot Alkaloids

§ The broad spectrum of bioactivity exhibited by ergot alkaloids is due to their structural similarity to natural neurotransmitters

8 6 NH H 9 10 5 4 H11 16 3 12 2 13 1 15 NH 14

Ergoline NH2 NH2 NHMe NH2 HO HO

N HO HO HO H OH OH OH

serotonin (5-HT) dopamine (DA) norepinephrine (noradrenalin) epinephrine (adrenalin)

§ Ergot alkaloid drugs generally act by mimicking (agonist) or blocking (antagonist) the binding of natural neurotransmitters to their receptors

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§ The majority of ergot alkaloid pharmaceuticals are semi-synthetically prepared from lysergic acid derivatives

OH Et2N O NH NH H O N H

Lysergic acid diethylamide (LSD) NH Ergometrine prevents post partum haemorrhage MOA: a-1A adrenergic agonist O Ph 5-HT2 agonist N N N H O O HO O NH O N HN O N N O NH OH O N O N H O N H H H H Br N NH NH H Ergotamine Cabergoline Bromocriptine migraine treatment Parkinson's disease Parkinson's disease MOA: 5-HT1B agonist MOA: D2 agonist Type 2 diabetes MOA: D2 agonist

Steph McCabe @ Wipf Group Page 8 of 25 3/27/2016 Clavine Alkaloids

Steph McCabe @ Wipf Group Page 9 of 25 3/27/2016 Clavine Alkaloids

OH OH OH N 8 N N HO N N N N N H H H H H H H H H HO AcO AcO H H H H H

N N N N N NH N H H H N H H H H agroclavine setoclavine penniclavine festuclavine elymoclavine fumigaclavine B fumigaclavine A fumigaclavine C

tetracyclic clavines

tricyclic clavines Clavine Alkaloids Rearranged clavines

OH OH O O 7 HN HN N NHMe 6 NHMe O O H H H H H

N N NH NH NH H H isochanoclavine-I chanoclavine-I rugulovasine A rugulovasine B Cycloclavine

OH CHO O N NHMe NHMe NMe2 H H H COOH N H HN HN O H H H H H H

NH NH NH N N H N N H H chanoclavine-I chanoclavine-II 6,7-seco-agroclavine H aldehyde paspaclavine clavicipitic acid aurantioclavine epoxyagroclavine

Steph McCabe @ Wipf Group Page 10 of 25 3/27/2016 Biosynthesis of Clavine Alkaloids

§ The first 5 steps in the biosynthetic pathway are common to all ergot alkaloids and are responsible for the formation of the core ergoline scaffold • Most diversification occurs late stage via functionalization of ergoline core however, in some fungi diversification can occur early on via short diverted pathways

COOH HN HN

decarboxylation N N H H clavicipitic acid aurantioclavine benzylic oxidation /aminocyclisation

CO2H CO2H CO2H DmaW EasF NH2 NH2 N prenyltransferase N-methyltransferase H SAM N OPP N N H H H L-tryptophan DMAPP DMAT N-Me-DMAT

ACIE, 2015, 54, 3004-3007 (aurantioclavine) J. Org. Chem., 1980, 45, 1117 (clavicipitic acid) Nat. Prod. Rep., 2011, 28, 496 Toxins, 2014, 6, 3281 Nat. Prod. Rep., 2014, 31, 1328

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O O HN O HN O

N N H H rugulovasine A rugulovasine B

??? O

OH O HN CO2H EasE oxidoreductase H HN EasC catalase EasD H oxidase N H H H N NH H NH N-Me-DMAT Chanoclavine-I Chanoclavine-I aldehyde last common precursor

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OH OH N H HO N H

N OH EasA_NI H N isomerase N H HO2C EasG H setoclavine N penniclavine N reductase H H H CloA H P450 spontaneous/ O monooxygenase isomerase NH lysergic acid N N HN H H H subclass agroclavine elymoclavine lysergic acid H O N NH HN N H tetracyclic H clavine H Chanoclavine-I EasA_Af EasG subclass reductase spontaneous H aldehyde H H reductase

NH NH NH festuclavine

N H N EasH H dioxygenase H EasG reductase NH NH cycloclavine

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EasL NH EasN NH NH (FgaPT1) N P450/ FAD H (FgaAT) H H H prenyltransferase monooxygenase HO O-acetyltransferase AcO AcO H H H H

N N N NH H H H festuclavine fumigaclavine B fumigaclavine A fumigaclavine C

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OH OH OH 8 N HO N N N N N N H N H H H H H H H H HO AcO AcO H H H H H

N N N N NH N N H H H N H H H H agroclavine setoclavine penniclavine festuclavine elymoclavine fumigaclavine B fumigaclavine A fumigaclavine C

tetracyclic clavines

tricyclic clavines Clavine Alkaloids Rearranged clavines OH OH O O 7 HN OHN N NHMe 6 NHMe O H H H H H

N N NH NH NH H H isochanoclavine-I chanoclavine-I rugulovasine A rugulovasine B Cycloclavine

OH CHO O N NHMe NHMe NMe2 COOH H H H HN N H HN O H H H H H H

NH NH NH N N N H H H N H chanoclavine-I chanoclavine-II 6,7-seco-agroclavine clavicipitic acid aurantioclavine aldehyde paspaclavine epoxyagroclavine

Steph McCabe @ Wipf Group Page 15 of 25 3/27/2016 Recent Synthetic Approaches to Clavine Alkaloids Clavicipitic Acid

COOH COOH § Clavicipitic acid is a rearranged clavine alkaloid that was isolated as HN 5 HN a mixture of naturally occurring cis and trans diastereomers from 7 C 3 Claviceps species of fungi. ( fusiformis and claviceps SD 58)

A B § Unusual azepinoindole core bearing two stereocentres presents an NH NH interesting synthetic challenge (-)-trans clavicipitic acid (-)-cis clavicipitic acid

JIA (2010) PARK (2007)

CO2H 6 SN2' Aminocyclization CO H HN 2 HN 7 catalytic 3 enantioselective * Pd catlyzed phase transfer Indole formation alkylation (99% ee) Heck/ NH1 Heck NH SN2' Aminocyclization coupling

7 steps, 34% overall yield trans 11 steps, ~20 % overall yield 7 steps, 7% overall yield cis

SHIBATA (2015) PIERSANTI (2014) Imine formation CO H Intramolecular CO2H 2 reductive HN HN amination 5 Ir catalyzed Friedal-Crafts 7 cyclodehydration 7 Alkylation 3 3 N-alkylation Rh(I)-catalyzed 1,2 addition of an NH N (±) H indole-4-pinacolboronic ester to an imine 9 steps (to CO2Me) 4 steps, 34% overall yield 15% overall yield (" ")

JOC, 2014, 79, 3255; JOC, 2010, 75, 7626; JOC, 2007, 72, 8115; Eur. J. Org. Chem., 2004, 1244; Chem. Eur. J., 2015, 11340

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HN 5 § Same azepinoindole core as Clavicipitic acid 7 C § Isolated in 1981 from the fungus penicillium aurantiovirens A B N H § Absolute Stereochemistry was determined to be 7R by Stoltz (based on X-ray analysis of an advanced intermediate) (-)-Aurantioclavine

alkenylation STOLTZ (2008) ELLMAN (2005) of N-alkylsulfinyl S 2 Mitsunobu/ Mitsunobu imine N Oxidative HN (94% de) HN 6 5 Kinetic 7 Resolution Stille formylation/ N-alkylsulfinyl C=O Addition N imine formation N H H 13 steps, <1% overall yield 6 steps, 27% overall yield

asymmetric allylic ISHIKURA (2009) amination TAKEMOTO (2014) (92% ee) Pictet-Spengler HN Suzuki- 6 HN 7 6 Miyaura H 7 coupling Deoxygenation Suzuki- Miyaura 2 N Indole formation H coupling N (±) H1 3 steps, 26% overall yield 16 steps, 13% overall yield

JACS, 2008, 130, 13745; OL, 2014, 16, 996; OL, 2010, 12, 2004; Eur. J. Org. Chem., 2009, 5752 Early racemic synthesis Chem. Pharm. Bull., 1985, 33, 2162; JOC, 1987, 52, 3319

Steph McCabe @ Wipf Group Page 17 of 25 3/27/2016 Recent Synthetic Approaches to Clavine Alkaloids Rugulovasine A & B

• Rugulovasine A and B are modified clavine alkaloids containing a spirolactone moiety

• They were isolated as a mixture of naturally occurring diastereomers from the fungus penicillium concavo-rugulosum • Both Rugulovasine A and B were isolated in racemic form and interconverted at room temperature • Interconversion is proposed to occur via a vinylogous Mannich reaction that proceeds through an achiral 2-alkoxyfuran intermediate

O NHMe O O O NHMe Me NHMe O 6 O D 5 10 11 C N A B H N N H H rugulovasine A rugulovasine B

MARTIN (2001) MARTIN (2001) JIA (2013) intermolecular intramolecular vinylogous vinylogous cyclocarbonylation O Mannich O Mannich O NHMe NHMe NHMe O O 5 5 O 10 Indole Mannich/ 10 Indole Mannich/ - 11 CN- nucleophilic 11 CN nucleophilic NHK addition SRN1 addition N Stille N N H coupling H H 8 steps 8 steps 5 steps 11% overall yield 30% overall yield 20% overall yield

JACS, 2001, 123, 5918; OL, 2013, 15, 3662 18

Steph McCabe @ Wipf Group Page 18 of 25 3/27/2016 Isolation of Ergot Alkaloid Cycloclavine

N 8 H 5 10

NH (+)-Cycloclavine

§ First isolated in 1969 from the seeds of the African morning glory (Ipomea hildebrandtii)

§ Structure elucidation, including relative and absolute stereochemistry (5R, 8S, 10S) was determined by X-ray crystallographic analysis of the methobromide salt 20 • Optical rotation [α] D = + 39 (pyr)

§ Therapeutic potential of cycloclavine remains underexplored (1 patent describes pesticidal properties) Ipomea hildebrandtii • “Cycloclavine and derivatives thereof for controlling invertebrate pests” (BASF, 2013)

Tetrahedron, 1969, 25, 5879 PCT Int. Appl. WO2014096238 A1, 2013

Steph McCabe @ Wipf Group Page 19 of 25 3/27/2016 Recent Synthetic Approaches to Clavine Alkaloids Cycloclavine

SZANTAY (2008) WIPF (2011) N-alkylation/ intramolecular aldol N-alkylation N N intramolecular methylene-cp DA Cyclopropanation 1,2 C=O Addition/ IMDAF

NH NH

7 steps, 1% overall yield 14 steps, 1.2% overall yield from Uhle's ketone derivative N 8 D H 5 E 10 C

CAO (2014) A B BREWER (2014) NH Aza-Cope Fragmentation/ Mannich (+)-Cycloclavine 1,3-dipolar cycloaddition N N Cyclopropanation Cyclopropanation

EDA addition Radical NH cyclization NH

12 steps (formal synthesis) 8 steps, 7% overall yield (formal synth.) 6% overall yield 14 steps, <1 % overall yield (total synth.)

Tetrahedron, 2008, 64, 2924; Tetradhedron Lett,, 2014, 56, 197; JOC, 2014, 79, 122; JACS, 2011, 133, 7704

Steph McCabe @ Wipf Group Page 20 of 25 3/27/2016 Szántay's Approach (2008)

N-alkylation/ Szantay (2008) intramolecular aldol

Cyclopropanation

H Br O N O N steps O 1. N OEt H EtO HO THF, 48% NH 2. LHMDS, THF OH NH O 4-bromo -70 °C, 50% Uhle's ketone

N N Me 4 steps, 14% CH2N2, Pd(OAc)2

CH2Cl2 32% (BRSM) NH NH

Tetrahedron, 2008, 64, 2924

Steph McCabe @ Wipf Group Page 21 of 25 3/27/2016 Brewer’s Approach (2014)

Fragmentation/ 1,3-dipolar cycloaddition N

Cyclopropanation

EDA addition NH Brewer

SnCl 4 CO Et OTBS TBS 2 OTBS EtO2C OH O EtO2C OH EtO C 2 O N 2 SnCl4 N N N N N CH2Cl2, 0 °C, N Piv 10 min, 80 % N N Piv Piv Piv

CO Et 2 N N EtO2C N H O N OTMS PhMe N DBU/ H O NH NH 0 °C-120 °C Piv 2 65% Piv deprotection Szantay's intermediate

Tetradhedron Lett,, 2014, 56, 197

Steph McCabe @ Wipf Group Page 22 of 25 3/27/2016 Cao’s Approach (2014)

Aza-Cope Mannich N

Cyclopropanation

Radical NH cyclization Cao

HO H O O N Ts Ts Ts O OH • N H N NHTs Br Br Br Br Br

FeCl3, CH2Cl2, N N NTs NTs Ts Ts reflux, 0.2 h, 83% NTs

Ts Ts Me N N N H H H isomerization 1) NaBH4 2) PhSSPh PhS deprotection Br methylation PBu3 n-Bu3SnH, AIBN, cycloclavine NTs benzene, reflux, 91% NTs NH

Szantay's intermediate JOC, 2014, 79, 122

Steph McCabe @ Wipf Group Page 23 of 25 3/27/2016 Wipf’s Approach (2011)

N-alkylation N intramolecular methylene-cp DA

Addition/ IMDAF

NH Wipf

1. MsCl, Et3N, CH2Cl2, 0 °C, 1 2. H N O NaH, DMF, rt, 12 h 1. µW, PhCF3, 195 °C, 1 h OH 67% (2 steps) 52% (72% brsm) TBSO N O OH 3. NaHMDS, THF, -78 °C N 2. TBAF, THF, rt, 85 % H then TBSCl

1. O N SnBu3 1. MeOC(O)Cl, 70 °C Boc LAH, THF 3 h, 71% n-BuLi, THF, -78 °C, 51% 66 °C, 30 min, O quant HN (±)-cycloclavine 2. LDA, THF, -78 °C, 1 h N H 2. 180 °C, PhCF3, µW, 30 min N then TMSCl (1.3 equiv) CO2CH3 44% (56% brsm) H CO2CH3 then Pd(OAc)2 (1.3 equiv) CH3CN, 12 h, rt 67%

Dr Filip Petronijevic JACS, 2011, 133, 7704

Steph McCabe @ Wipf Group Page 24 of 25 3/27/2016 Acknowledgements

• Prof. Peter Wipf • Group Members Past and Present • Mass Spec, NMR, X ray facilities • Mary E. Warga Predoctoral Fellowship • Arts & Sciences Fellowship

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