Approaches to the Synthesis of Macquarimicins and Cochleamycins
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1 Ac Macquarimicin A Cochleamycin A Approaches to the Synthesis of Macquarimicins and Cochleamycins Drew Adams Friday Seminar March 18, 2005
2 Isolation and Activity Ac Isolated in 1995 from Micromonospora bacteria Macquarie University, Sydney, Australia Weak activity against anaerobes Isolated in 1992 from Streptomyces bacteria Nishimeya-cho, Aomori, Japan Weak activity against Gram-positive bacteria Cytotoxic against P388 leukemia line (0.3 µg/ml) Selective but weak activity against N-SMase, as outlined below Cytotoxic against a variety of tumor lines Macquarimicin A Cochleamycin A Jackson, M. J. Antibiotics, 1995, 48, gita, T. J. Antibiotics, 1999, 52, 670. Shindo, K. J. Antibiotics, 1996, 49, N (C 2 ) n C 3 P N (C 2 ) 12 C 3 sphingomyelin Neutral, Mg ++ -dependent Sphingomyelinase For more on ceramide signalling pathways: gita, T. J. Antibiotics, 1999, 52, 531. hanian, J. Cell. Mol. Life Sci, 2001, 58, Andrieu-Abidie, N., Biochim. Biophys. Acta, 2002, 1585, 126. N (C 2 ) n C 3 (C 2 ) 12 C 3 ceramide IL-1β, PGE 2 inflammation cell proliferation apoptosis
3 Derivatives Michael Reaction S N 2 alkylation Macquarimicin A Macquarimicin B Macquarimicin C Ac Cochleamycin A Reduction; S N 2 alkylation Ac Cochleamycin B Tadano, JACS, 2004, 126,
4 Biosynthetic Proposal Ac Ac Feeding studies indicate incorporation of six acetate subunits and a single propionate. linear polyketide precursor Cochleamycin A allylic oxidation Ac IMDA C Ac Knoevenagel Condensation Ac Ac Knoevenagel Condensation TADA Shindo, K. J. Antibiotics, 1996, 49, 244. Cochleamycin A
5 Biosynthetic Proposal, Tested Me + Me Me Me Macquarimicin A FR (see also exacyclinic Acid) Pd(0) (Stille) TBS TBS Xc 1. RT 2. KMDS, -78 C TBS TBS C Diels-Alder selectivity poor Cyclization of medium rings is difficult using reversible reactions. various Knoevenagel conditions Sorenson, JACS, 2003, 125, macrocycle
6 A Summary of Approaches R R R R R IMDA TADA Tatsuta (2003, Cochleamycin) Roush Tadano Paquette Tadano (2003, Macquarimicins) Roush (2004, Cochleamycin) (Evans) Tatsuta, J. Antibiotics, 2003, 56, 584. Roush, L, 2003, 5, Tadano, L, 2001, 3, Paquette, L, 2002, 4, 253. Paquette, JC, 2004, 69, 6441.
7 Synthesis of IMDA Substrates a, b 85% I TBDPS c 83% TBDPS d 80% TBDPS TBDPS TBS f, g 63% TBDPS e h, i 78% TBDPS TBS j, k 64% TBDPS TBS a) TBDPSCl, imid., DMAP; b) Cp 2 Zr()Cl, C 2 Cl 2 ; I 2 ; c) Pd(PPh 3 ) 2 Cl 2, CuI, NEt 3 ; d) Mn 2, C 2 Cl 2 ; e) diisopropyl(s,s)-tartrate-(e)- crotylboronate, PhMe, -78 C; f) TBSCl, imid.; g) 9-BBN, TF, 0 C, then aq. 2 2, aq. Na; h) Zn, Cu(Ac) 2 2, AgN 3, Me/ 2 ; i) DMP, pyr., wet C 2 Cl 2 ; j) diethyl (N-methoxy-N-methylcarbamoylmethyl)phosphonate, Na, TF; k) DIBAL-, TF, -78 C Roush, L, 2003, 5, 4725
8 Key IMDA Reactions Paquette PMP PMB cat. BT, PhMe, 195 C, 26 h Piv C PMB Piv moderate yield, one isomer PMP MM Tatsuta TBDPS R R R R = MM Yb(fod) 3, BT, xylene, 140 C, 4 h high yield, one isomer TBDPS C MM MM Roush TBDPS TBS cat. BT, PhMe, 160 C, 16 h 83% (minor isomer, 3%) C TBS TBDPS PMB Tadano PMB cat. BT, PhMe, 150 C C Tr 75%, single isomer Tr
9 IMDA Diastereoselectivity Tadano C R C 3 C PMB PMB PMB Endo I: Minimizes allylic strain Tr 75% Tr C PMB C 3 C 3 Endo II: Allylic strain buildup PMB C Tr not observed Exo TS not feasible given the orientation of the (E, Z) diene. Tadano, L, 2001, 3, 3029
10 Roush's Lewis Acid Activation Experiments products of stepwise reaction TBDPS TBS 0.6 eq. MeAlCl 2, DCM, -78 to -23 C 66% C TBDPS TBS C TBDPS TBS C TBDPS TBS products of stepwise reaction TBDPS TBS 0.6 eq. MeAlCl 2, DCM, -78 to -20 C 57% mix of four products C TBDPS TBS C TBDPS TBS unidentified isomers Increasing activation of the dienophile hinders diastereocontrol: stepwise pathways preferred. Roush, L, 2003, 5, 4725.
11 Tadano's Diverse IMDA Targets PMB BT, PhMe, sealed tube, 185 C, 11 days, PMB five unidentified isomers 71% C C Tr Tr PMB PMB BT, PhMe, sealed tube, 150 C, C 81 %, plus minor isomers MM TBS TBS MM PMB cat. BT, Bu, 150 C PMB C TBS PMB TBS 66%, single isomer TBS TBS Bu TBS TBS Bu Tadano, L, 2001, 3, 3029.
12 Tadano's Knoevenagel Macrocyclization Efforts C TBS TBS PMB Bu Variety of Amines and Lewis Acid/Amine pairs Bu 2 C PMB TBS TBS C PMB TBS MgBr 2 Et 2, EtS, Et 2 64% C PMB TBS Variety of Amines and Lewis Acid/Amine pairs PMB TBS MM Route abandoned in favor of TADA approach. Tadano, L, 2001, 3, 3029.
13 Paquette's rganometallic Macrocyclization Efforts PMB PMB PMB Piv PMP C a-d, 60% yield I Kishi-Nozaki or SmI 2 PMP PMP PMB PMB e-h, 44% yield various metathesis catalysts PMP PMP a) CBr 4, PPh 3, pyr., C 2 Cl 2, 0 C, 98%; b) n - BuLi, TF, -78 C, 86%; c) I 2, morpholine, Ph, C, 90%; d) PCC, NaAc, seives, C 2 Cl 2, 78%. e) Ph 3 PC 3 + Br -, n-buli, TF, -78 C, 76%; f) n-buli, TF, -78 C, 76%; g) PCC, NaAC, seives, C 2 Cl 2, 76%; h) C 2 CMgBr, TF, -78 to 0 C, 96%.
14 Paquette's Macrolactonization Efforts Me N TBS MEM PMB F 3 C P 1. F 3 C Br 2. NaMDS, TF, -10 C 79% S B S Cl C 2 Cl 2 72% Me All Br N TBS PMB 1. Pd(Ac) 2, Ph 3 P, dimedone, TF 2. 2,4,6-Cl 3 C 6 2 CCl, NEt 3, TF; DMAP, PhMe, reflux 73% for two steps Me N TBS PMB PMB TBS t-buli, -78 C or Bu 3 SnTMS, BnEt 3 NCl, DMF or SmI 2, MPA, TF Aldehyde equally unreactive (Kishi-Nozaki conditions, Reike zinc) Me N Br TBS PMB 93-97% 0 % Paquette, JC, 2004, 69, 6441.
15 Tatsuta: First Synthesis of Cochleamycin A MM MM TBDPS a-b; 68% TBDPS Et 2 C C c, d; 72% MM MM MM MM e, f; 64% C 2 Et MM 1. CCl 2, DMS, NEt 3, C 2 Cl 2 ; Br C 2 Et MM MM MM 2. SmI 2, TF, 0 C, 15 min 61% over two steps MM MM MM MM MM C 2 Et g - i; 56% j - m; 35 % C 2 Cochleamycin A a) triethyl phosphonoacetate, Na, TF, -30 C, 80%; b) 2, Rh-C, PhMe, 85%; c) TBAF, TF, 50 C, quant.; d) LDA, TF, -78 C; CBr 4, 72%; e) IBX, PhMe, DMS, 89%; f) PhSeCl, LMDS, TF; then 2 2, 0 C, 62%; g) NaB 4, CeCl 3 7 2, Et, 0 C, 70%; h) Cl, Et; i) Li, 2, TF, 60 C, 80% over two steps; j) ethyl ethynyl ether, [RhCl 2 (p-cymene)] 2, DMF, 0 C, 68%; k) CSA, TF, 83%; l) Mn 2, EtAc, 85%; m) NaAc, Ac 2, 60 C, 72% Ac Tatsuta, J. Antibiotics, 2003, 56, 584.
16 Kita's Acylation Method Et L Cl Ru Et L Cl Ru Et Cl R [{RuCl 2 (p-cymene)]} 2 L Cl Ru Et R Cl esters, amides, etc. Et R R prominent side reaction R R Kita, J. Chem. Soc. Perkin 1, 1993, 2999.
17 A Summary ofapproaches R R R R R IMDA TADA Tatsuta (2003, Cochleamycin) Roush Tadano Paquette Tadano (2003, Macquarimicins) Roush (2004, Cochleamycin) (Evans) Tadano, JACS, 2004, 126, Roush, L, 2004, 6, Beaver, Ph.D. dissertation, arvard U., 2002
18 Synthesis of TADA Substrates Sonigashira coupling/partial reduction no longer attractive; Stille approach now dominant oveyda catalyst MesN Cl Cl Ru NMes a b TBDPS TBDPS 85% Me TBDPS Ph Ph Me I d, e, f 46% Me TBDPS c 89% g, h, i 56% Me TBS TBS I j, k 82% Et TBSTBS I vinyl iodide fragment a) ( d Ipc) 2 -B-allyl, TF, -78 C; b) methyl acrylate, 1.5 mol% oveyda catalyst, C 2 Cl 2, reflux; c) PhC, tbuk, TF, 0 C; d) (F) 3 Et 3 N, MeCN, 40 C; e) S 3 pyr, DMS, ipr 2 NEt, C 2 Cl 2, 0 C; f) CrCl 2, CI 3, dioxane/tf; g) 80% Ac, TF, 95 C; h) Amberlite IRA- 400(), Me; i) TBSTf, 2,6-lutidine, C 2 Cl, -78 C; j) DIBAL-, -78 C; k) ethyl diazoacetate, SnCl 2, C 2 Cl 2. Roush, L, 2004, 6, 2043
19 Synthesis of TADA Substrates Sonigashira coupling/partial reduction no longer attractive; Stille approach now dominant TMS a 66% TMS b, c 76% TBS d 94% h, i 76% I TBS Me e, f, g 81% I TBS TBS Pd(PPh 3 ) 4, CuCl, TF/DMS (1:1) SnMe 3 TBS vinyl stannane fragment Et TBSTBS 85% I Et TBS TBS a) ( d Ipc) 2 -B-allyl, TF, -78 C; b) TBSTf, 2,6-lutidine, C 2 Cl 2, -78 C; c) 9-BBN, TF; then aq. Na/ 2 2 ; d) n-buli, TF, -50 C, then I 2 ; e) o-nitrobenzenesulfonylhydrazide, Et 3 N, TF/i-Pr (1:1); f) S 3 *pyr, DMS, ipr 2 NEt, C 2 Cl 2, 0 C; g) Trimethyl phosphonoacetate, LiCl, NEt 3, MeCN; h) DIBAL-, C 2 Cl 2 ; i) MeLi, Et 2, -40 to 23 C; n-buli, -78 C; then Me 3 SnCl, TF, -78 C. Roush, L, 2004, 6, 2043
20 Synthesis of TADA Substrates Group methodology, Suzuki coupling employed in Krista Beaver's approach. Et SPh TMS Bn N Sn N Tf Tf Bn 10 mol %, -78 C 95:5 anti:syn, 93% ee Et SPh 5 steps, 40% E/Z = 5:1 I TBS TBS TMS Bn N N N Cu N t-bu t-bu 7.5 mol % (CF 3 ) 2 C, 83% 98:2 anti:syn, 99% ee 2+ 2 SbF 6 N Bn N 10 steps, 28% pure (E) I TBS TES 2+ TMS TMS N N Cu N 2 SbF 6 t-bu Bn Ph Ph C 2 Cl 2, -95 to -78 C, 83%, 99% ee t-bu Bn 10 steps, 12% Piv TES B() 2 PMB Beaver, Ph.D. thesis, arvard, 2002
21 Tadano's First TADA Target Me 2 C TBS PMB ptional: 1. F pyr., pyr., TF 2. MMCl Then: Me 2 C R PMB 1. Pd(PPh 3 ), dppe, TF, 84% 2. NaMDS, TF, -78 C; PhSeCl, PhMe 3. mcpba, C 2 Cl % TBS Formed via Stille coupling Me, PhMe, 110 C, 98% (90% over 3 steps) Me R = TBS or MM R PMB PMB PMB PMB Me 2 C R R Me 2 C R R Me 2 C R BT, 130 C, PhMe Me 2 C R R desired isomer R Exclusively (Z) 0% 29% 29% <10%? 10% <10%? R = TBS R = MM (worse, efforts to deprotect failed) Tadano, JACS, 2004, 126, 11254
22 Tadano's Second TADA Target PMB PMB 1. F pyr., pyr. 2. ipr 2 NEt, Me Me 2 C TBS TBS 1. PhSeCl, NEt 3, C 2 Cl 2, -78 C 2. mcpba, C 2 Cl 2, -50 C PMB PMB 1. TESTf, lutidine 2. DDQ, p 7 buffer 3. DMP, NaC 3 4. PPTS, Me 66% BT, PhMe, 130 C 47% over five steps Macquarimicin A "The TADA substrate showed a complicated 1 NMR spectrum, making determination of the E/Z ratio extremely difficult. We attribute this complication to the presence of tautomers such as hemiketal forms and/or rotamers..." Tadano, JACS, 2004, 126, 11254
23 TADA Stereoselectivity PMB PMB PhMe, BT 130 C PMB one isomer good yield only transition state in which allylic strain minimized E/Z isomerization facile PMB PMB A(1,4) strain buildup 6π cyclization? Tadano, JACS, 2004, 126, 11254
24 Tadano: Macquaramicins B and C Me TF, 2 Me 83 % Macquarimicin A Macquarimicin B CSA, C 2 Cl 2, quant. Macquarimicin C Tadano, JACS, 2004, 126, 11254
25 Roush's TADA Efforts Me 2 C TBS TBS TBS 1. PPh 3, I 2, imid., C 2 Cl 2, 0 C 2. Cs 2 C 3, TF 90% Me 2 C TBS TBS TBS 1. NEt 3, PhSeCl, C 2 Cl 2 ; mcpba, CCl 2, 52% 2 : 1 Z/E 2. Thermal or Lewis Acid activation Me 2 C TBS TBS TBS TES R R = TES 1. (F) 3 NEt 3, NEt 3, C 3 CN, 45 C 2. ipr 2 NEt, Me 3. TESCl, imid, DMF 4. NEt 3, PhSeCl, C 2 Cl 2 ; mcpba, CCl 2, -50 C "...a complex mixture..." 47% Ac TES BT, PhMe, 125 C 69% TES 1. PPTS, Me 2. NaAc, Ac 2, 60 C 60% Roush, L, 2004, 6, 2043 Cochleamycin A
26 Evans' TADA Approach TBS 1. Et 2 CCl, pyr. TBS 1. KMDS, PhSeCl, -10 C; Davis oxaziridine, NaC 3, CCl 2 2:1 Z/E TBS Et 2 C 2. Pd(Ac) 2, dppe PMB 79% Et 2 C TES PMB 2. PhMe, 150 C 67% Et 2 C PMB TES TES R TBS R = PMB 1. F pyr, pyr, TF 2. K 2 C 3, Me 3. NEt 3, PhSeCl 4. Davis oxaziradine, NaC 3, PhMe 47% TBS PMB Et TES lactonization impossible TBS PhMe, 125 C or Ph, -20 C quant. PMB Cochleamycin A Beaver, Ph.D. dissertation, arvard U., 2002
27 Evans' TADA Approach TBS TBS Et 2 C PMB Base, Light, eat, Nucleophiles C 2 Et PMB Calculations suggest thermodynamic preference strongly opposed to desired geometry. TES TES TBS NaCNB 3 Et C 2 Et More vigorous conditions over-reduced or decomposed a model system. PMB TES Beaver, Ph.D. dissertation, arvard U., 2002
28 Summary of TADA Reactions TBS TBS PhMe, 150 C 67% Evans Z / E = 2 : 1 Et 2 C TES PMB Et 2 C TES PMB TBS TBS Roush Z / E = 2 : 1 Me 2 C TBS TBS Thermal or Lewis Acid activation Me 2 C TBS TBS PMB PMB Tadano Z / E > 20 : 1 Me 2 C R R BT, PhMe 130 C Me 2 C R R R = TBS R = MM 0% 29%
29 Summary of TADA Reactions TBS TBS Evans R PhMe, 125 C or Ph, -20 C quant. PMB R = PMB TES TES Roush R R = TES BT, PhMe, 125 C 69% TES PMB PMB Tadano BT, PhMe, 130 C 47% over five steps
30 Conclusions ne completed synthesis using IMDA (Tatsuta) Closing 10 membered ring after IMDA challenging: nly a Samarium-mediated Reformatsky reaction succeeded. Two completed syntheses using TADA (Tadano, Roush) Palladium π allyl and malonate alkylation effectively closed macrocycle. Protecting group choices far more important than expected: Evans carried out a TADA that Roush and Tadano could not, But Roush and Tadano achieved the TADA that led swiftly to the natural product.
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