Recent Total Syntheses! Published in ature! Eric ewcomb 8/21/2011! 2 S 3 2 2
ature Then and ow! First published ov. 4th, 1869 First issue states two objectives: 'The objective which it is proposed to attain by this periodical may be broadly stated as follows. It is intended, First, to place before the general public the grand results of scientific work and scientific discovery; and to urge the claims of science to move to a more general recognition in education and in daily life.' 'Secondly, to aid scientific men themselves, by giving early information of all advances made in any branch of natural knowledge throughout the world, and by affording them an opportunity of discussing the various scientific questions which arise from time to time.' In 2010 the acceptance rate was 7.9% (10.287 submitted and 809 accepted) In 2010 the impact factor was 36.1 Much more biologically relevant chemistry is published than synthetic Broader interest is a major factor in publication consideration Broader interest is determined solely by ature editors, not referees
ollective synthesis of natural products by means of organocascade catalysis! 2 2 2 Jones, S. B.; Simmons, B.; Mastracchio, A.; MacMillan, D. W.. ature 2011, 475, 183.
ow nature assembles molecules?! 2 Preakuamminicine ommon tetracyclic core orfluorocuraine Et 2 Didehydrosecodine Strychnine Jones, S. B.; Simmons, B.; Mastracchio, A.; MacMillan, D. W.. ature 2011, 475, 183. 2 Vincadifformine
MacMillanʼs bread and butter: iminium catalysis! Boc X Im Im organocascade catalysis Boc common tetracycle natural products Boc R 2 Boc R 2 Boc X Path A t-bu Se Boc [4+2] 1-ap Boc Se Se t-bu 1 Im 1-ap R' R' = Boc R 2 R' X= R 2 Path B X= Boc Boc X t-bu 2 Im 1-ap Boc X Boc common tetracycle Jones, S. B.; Simmons, B.; Mastracchio, A.; MacMillan, D. W.. ature 2011, 475, 183.
Synthesis of (-)-strychnine! (1) (Ph 3 P) 3 Rh tol., Ph, 120 (2) 2, Et 3, tol. -45 to RT, then, -30 to RT (1) DBU, K 2 3 DMF, RT I Br I (3) DIBAL, DM -78 to RT, then TFA 61% yield, over three steps PMB 2 (2) DIBAL, DM, -78 67% yield, over two steps PMB Pd(Ac) 2 (25 mol%) Bu 4, a 3 EtAc, RT 58% yield PMB PhS, TFA, 45 66% yield aac, Ac 2 Ac, malonic acid 120 69% yield AME? (-)-strychnine Jones, S. B.; Simmons, B.; Mastracchio, A.; MacMillan, D. W.. ature 2011, 475, 183.
Synthesis of (-)-akuammicine! PhS, TFA, 60 Br I K 2 3, DMF, RT I PMB 2 91% yield 2 76% yield 2 Pd(Ac) 2 (20 mol%) a 3, Bu 4, 65 47% yield 2 (-)-akuammicine Jones, S. B.; Simmons, B.; Mastracchio, A.; MacMillan, D. W.. ature 2011, 475, 183.
Synthesis of (+)-aspidospermidine &! (+)-vincadifformine! Boc 3-steps Boc ent-im cat. (20 mol%) Boc (1) Ph 3 P 3 I, n-buli TF, 0, then Ac ab 3, 0 (2) TFA, DM, RT 61% yield Bn I Se (Ph 3 P) 4 Pd, Et 3 tol. 80-40 to RT, tol 83% yield, 97% ee Bn Pd() 2, 2 (200 psi), EtAc, RT (3) Br K 2 3, DMF, RT 73% yield, over three steps I Bn 65% yield Bn 98% yield DM, DMS () 2 n-buli, 2 TF, -78 to RT (+)-aspidospermidine 65% yield 57% yield 2 (+)-vincadifformine Jones, S. B.; Simmons, B.; Mastracchio, A.; MacMillan, D. W.. ature 2011, 475, 183.
Synthesis of (+)kopsinine & (-)-kopsanone! Bn Boc Et 3, DM, TMSI 0, then PPh 3 Br 40, then DM TF, Kt-Bu, 0 58% yield Bn (1) 2, Et 3, tol -45 to RT, then, -30 to RT (2) Pd/, 2 EtAc Et, 0 69% yield, two steps Bn 2 S 2 Ph R Raney i Et, 70 1, 130 Ph, 100 86% yield R = S 2 Ph Bn 2 83% yield 2 (+)-kopsinine B 200 2 neat 74% yield two steps (-)kopsanone Jones, S. B.; Simmons, B.; Mastracchio, A.; MacMillan, D. W.. ature 2011, 475, 183.
ollective Synthesis verview! (-)-strychnine 2 (-)-akuammicine (+)-aspidospermidine 12 steps 6.4% overall yield 10 steps 10% overall yield 9 steps 24% overall yield Syntheses are short and efficient "ollective synthesis" concept not new, but likely helps broader interest 2 (+)-vincadifformine 11 steps 8.9% overall yield 2 (+)-kopsinine 9 steps 14% overall yield (-)kopsanone 11 steps 10% overall yield
Total synthesis of a chlorosupholipid cytotoxin associated with seafood poisoning! S 3 ilewski,.; Geisser, R. W.; arreira, E. M. ature 2009, 457, 573.
Attempted Synthesis! 2 Et Et 4 3 DM, 0, 45 min 68% yield 2 Et (1) DIBAL, ethylbenzene 0, 10 min, 72% yield (2) TBS, imid. DM, 0 to RT, 30 min 87% yield TBS (1) s 4 (5 mol%), M acetone/ 2, RT, 19h 68% yield (2) DAB, (F 3 S 2 ) 2-78, 10min, then diol, -78 to RT, 15h 75% yield (96% BRSM) (+)-SA (cat), RT, 3 h 98% yield R R = TBS R = (1) () 2, DMS, Et 3 DM, -78 to RT, 1.5h (2) Br Ph 3 P TBS 6 n-buli, TF -78 to RT, 30min 62% yield over two steps 4.2:1 Z/E 6 TBS TMS, DM, EtAc 11.5 h 39% yield 31% recovered SM 4% minor product! (1) Et 4 3, DM 0, 10 min 51% yield (2) (+)-SA, 6 12 h, 80% yield TBS!!! 6 (1) PhI(Ac) 2, TEMP DM, RT, 16.5 h (2) r 2, 3 TF, 65 ame? 49% over two steps!!! 6 S 3 py TF, 30 min 27% yield 66% BRSM S 3!!! ilewski,.; Geisser, R. W.; arreira, E. M. ature 2009, 457, 573.
o match! 1 MR spectral data did not match natural product S 3!!! 2D 1 MR and 1 -heteronuclear coupling experiments determined relative configuration of product synthesized S 3 S 3 Desired Stereochemistry ilewski,.; Geisser, R. W.; arreira, E. M. ature 2009, 457, 573.
o match! TMS 6 TBS TMS R TMS 39% R R S 3 Undesired Stereochemistry TMS R 4% R S 3 Desired Stereochemistry ilewski,.; Geisser, R. W.; arreira, E. M. ature 2009, 457, 573.
Revision and success! 6 7:1 Z/E (Improved from 4.2:1) TBS TMS TMS, DM, EtAc, 9 h 43% yield (73% BRSM) R 6 TBS ( 5 2 ) 4 3, DM -78, 2 h 93% yield, d.r. = 10:1 R (+)-SA (cat), RT, 3 h 98% yield R = TBS R = TEMP (20 mol%) PhI(Ac) 2 R DM, RT, 16.5 h 6 r 2, 3, TF, 65 47% yield over two steps 6 S 3 pyridine TF, 20 min 99% yield S 3 (±)-chlorosulpholipid ilewski,.; Geisser, R. W.; arreira, E. M. ature 2009, 457, 573.
Synthesis of a chlorosulpholipid cytotoxin overview! S 3 Racemic synthesis 10 steps 1.15% yield of desired diastereomer Short synthesis but racemic Proposed anchimeric participation of chloride could prove very important in the synthesis of other polychlorinated structures
Total synthesis of marine natural products without using protec6ng groups! Baran, P. S.; Maimone, T. J.; Richter, J. M. ature 2007, 446, 404.
Approaches to chemical synthesis: selling point! The biosynthetic route Function-oriented free Enzymatic processes PP Ambiguine The Phil Baran approach Target-oriented free o enzymes Target-oriented needed "Standard" chemists R X Baran, P. S.; Maimone, T. J.; Richter, J. M. ature 2007, 446, 404.
Total synthesis of (- )- hapalindole U & (+)- ambiguine! R LMDS; u(ii)-2-ethylhexanoate R AME? Ac Pd P Ar Ar Pd Ar Ar P Ac Ar = o-tolyl (5 mol%) Four Steps from p-menth-1-en-9-ol (37% yield) R = or Br TF, -78 to RT, 5 min 61% yield (R = ) 50% yield (R = Br) a, TBAB Et 3, DMF, 80, 5 h 65% yield (1) 4 Ac, ab 3 /TF, µw (150 ) 2.5 min; then 2, DMT DMAP, MM, DM, 2 h, RT (2) 2, Et 3, DM, 0 60% yield over two steps (-)-hapalindole U Baran, P. S.; Maimone, T. J.; Richter, J. M. ature 2007, 446, 404.
Total synthesis of (- )- hapalindole U & (+)- ambiguine! t-bu, DM -78, 12 min; prenyl-9-bb -78, 30 min 60% yield B ß-face attack R B R = t-prenyl hv, Et 3 Ph, 5 h 63% BRSM B R B R (+)-ambiguine R = t-prenyl R = t-prenyl Baran, P. S.; Maimone, T. J.; Richter, J. M. ature 2007, 446, 404.
Total synthesis of (- )- fischerindole I & (+)- welwi6ndolinone A! LMDS; u(ii)-2-ethylhexanoate TF, -78 to RT, 20 min 62% yield (1) Montmorillonite K-10 µw (120 ), 6 min 57% yield BRSM (2) 4 Ac, ab 3 3 A MS, /TF )), 18 h, 42% yield 2 2, DMT DMAP, MM DM, RT, 30 min; Et 3, 2 DM, 0, 10 min 98% yield DDQ, 2 TF, 0, 30 min 92 % yield F taut. F (-)-fischerindole I Baran, P. S.; Maimone, T. J.; Richter, J. M. ature 2007, 446, 404. XeF XeF 2, 2 F, RT, 5 min 44% yield (+)-welwitindolinone A 2
- free total synthesis overview! (-)-hapalindole U (+)-ambiguine (+)-welwitindolinone A (-)-fischerindole I 8 steps 7.61% yield 10 steps 2.88% yield BRSM 8 steps 0.94% yield BRSM 7 steps 2.14% yield BRSM Very efficient in terms of step count -free (broader interest?) reative approach to this family Baran, P. S.; Maimone, T. J.; Richter, J. M. ature 2007, 446, 404.
The total synthesis of (- )- cyanthiwigin F by means of double cataly6c enan6oselec6ve alkyla6on! Enquist, J. A.; Stoltz, B. M. ature 2008, 453, 1228.
(-)-cyanthiwigin F: Retrosynthesis! Pd-cuprate enol triflate coupling radical-induced cyclization single pot RM/cross-metathesis egishi-coupling double catalytic enantioselective alkylation Enquist, J. A.; Stoltz, B. M. ature 2008, 453, 1228.
(-)-cyanthiwigin F: Synthesis! (1) Allyl alcohol a, Ph reflux AME RX? (2) K 2 3, I acetone, reflux 51% yield aisen-dieckmann 1:1 mixture of racemic:meso diastereomers Ph 2 P Pd(dmdba) 2 Et 2, RT 78% yield t-bu (R,R) 99% ee d.r. = 4.4:1 meso Enquist, J. A.; Stoltz, B. M. ature 2008, 453, 1228.
(-)-cyanthiwigin F! (R,R) (R,R) (R,R) 81% yield (R) (S,R) (R) meso-(r,s) meso-(r,s) 18% yield (R,S) (S) (S) (S,S) (S,S) (S,S) <1% yield Enquist, J. A.; Stoltz, B. M. ature 2008, 453, 1228.
(-)-cyanthiwigin F: Synthesis! KMDS Ph(Tf) 2 TF, -78 73% yield Tf Zn, TMS 1,2-dibromoethane I TF, 65 then Ph(PPh 3 ) 4 78% yield 2 Ru i-pr (10 mol%) t-bus AIB B Ph, 60 ; ab 3, TF/ 2 51% yield Ph, 80 57% yield (1) KMDS Ph(Tf) 2 TF, -78 60% yield (2) i-prmg u, TF; Pd(dppf) 2 63% yield Enquist, J. A.; Stoltz, B. M. ature 2008, 453, 1228. 1.8 : 1
(-)-cyanthiwigin F: verview! (-)-cyanthiwigin F 9 steps 2% yield 99% ee Efficient in terms of step count -free synthesis Double catalytic enantioselective alkylation sets quaternary centers early Enquist, J. A.; Stoltz, B. M. ature 2008, 453, 1228.
Five points on publishing syntheses in ature! 1. Broader intrests matter 2. Step count is king 3. Yield does not matter 4. Biological relevance can help 5. Even with 1-4, one still needs novelty