An Analysis of the Total Syntheses of Aphidicolin

An Analysis of the Total Syntheses of Aphidicolin An Evans Group Afternoon Seminar Krista Beaver March 20, 1998 A B D C Aphidicolin Isolated from the fungus Cephalosporium aphidicola (esp, Chem. Comm.1972, 1027) Structure determined by X-ray crystallography and chemical degradation Demonstrated activity against DNA viruses and human and murine neoplastic cell lines; acts via inhibition of DNA polymerase α (Cell 1981, 23, 647) Proposed Biosynthesis PP PP + PP Aphidicolin anson, JCS Perkins I1988, 1477 andout 01 3/23/98 11:02 AM

Endgame Strategies - An Early Approach 3 S + I -, Na 1. K, 2 2. acetone, + Cl, 74% + 42% 28% esp, JCS Perkins I 1973, 284 Endgame Strategies - An Improvement C 2 1. Tf 2, di-t-butyl-4-methylpyridine (100%) 2. Pd 0, C, (75%) m-cpba (90%) C 2 1. LA, TF, reflux (100%) 2. ion exchange resin,, reflux (100%) andout 02 3/20/98 11:06 AM verall yield was improved to 67% from 31% A. B. Smith III, JCS Perkins I 1991, 969

McMurry - Retrosynthetic Analysis McMurry Synthesis - A Robinson Annulation (C 2 ) 2 p-ts (80%) 1. Li, N 3, then TMS-Cl, Et 3 N (97%) 2. C 3 Li, then C 2 1. L-Selectride 2. acetone, p-ts (85%) Na, trace t-amyl alcohol (95%) 1. LDA, then methallyl iodide (89%) 2. s 4, NaI 4 dioxane/ 2 (86%) J. E. McMurry JACS 1979, 1330 andout 03 3/20/98 2:14 PM

McMurry - Completion of the Synthesis 1. LA (95%) 2. EtC=C 2 g(ac) 2 (90%) 360 C (20%) C LA, then p-tscl, pyridine (60%) Ts Aphidicolin Na 2 Fe(C) 4 NMP (30%) J. E. McMurry JACS 1979, 1330 Trost - Retrosynthetic Analysis TMS TMS andout 04 3/20/98 11:10 AM

Trost - A Vinyl Cyclopropane Rearrangement 1. SPh 2 2. PhSeSePh, NaB 4 3. C 3 (TMS)C=NTMS (50%) TMS FVP, 610 C (97%) TMS 8 1. Pd(Ac) 2, (73%) 2. Li, N 3,, then TMS-Cl (82%) TMS 8 2:1 Diastereoselection (α:β at C8) Trost, JACS 1979, 1328 Trost - Completion of the Synthesis TMS n-buli, MPA, then allyl iodide (35%) 1. thexyl borane then Na, 2 2 (57%) 2. PCC, then K, (54%) PCC (87%) 1. DP, p-ts 2. 2 NN 2, K, 140 C (91%) 3. p-ts, acetone (78%) andout 05 3/20/98 11:11 AM Trost, JACS 1979, 1328

Bettolo and Lupi - Retrosynthetic Analysis Bn Bn Bn Bn Bn Bn Bettolo and Lupi - [2+2] Cycloaddition 1. Na, BnBr 2. +, 2 (90%) 3. C 2 Et, Na Bn Bn MVK (75%) Et 3 N Bn Bn allene, hv (86%) Bn Bn 1. Na, CS 2, I (72%) 2. NaB 4 (91%) 3. 140 C (90%) Bn Bn 1. C 2 C 2, p-ts (80%) 2. 3 3. NaB 4 4. Cl 5. Na (76%) Bn Bn andout 06 3/20/98 11:13 AM Bettolo, Lupi, CA 1982, 371 Bettolo, Lupi, CA 1983, 1922 Bettolo, Lupi, CA 1988, 872

Bettolo and Lupi - Completion of the Synthesis Bn Bn MsCl, NaC 3 (97%) Bn Bn 1. PCC (81%) 2. Li/N 3 (69%) Corey's Intermediate Bettolo, Lupi, CA 1982, 371 Bettolo, Lupi, CA 1983, 1922 Bettolo, Lupi, CA 1988, 872 van Tamelen - Retrosynthetic Analysis Ms C 3 C 3 C 3 Bn andout 07 3/20/98 11:14 AM

van Tamelen - A Biogenetic Approach C 3 C 3 C 3 NBS, then K 2 C 3, (33%) 1. LiNEt 2 (57%) 2. V(acac) 2, 3. BnI, Na (90%) Bn FeCl 3 C 3 1. TrisNN 2, p-ts (70%) 2. n-buli, TMEDA (82%) 1. Li, TF-Et 2. Cl-Et 3. p-ts, acetone (55%) Bn van Tamelen, JACS 1983, 142 Van Tamelen - Completion of the Synthesis benzene, reflux, (86%) 1. Pt black (90%) 2. Pb(Ac) 2, 2, pyridine (28%) Ms 1. CaC 3, 2 -acetone (60%) 2. Cr 3 -pyr (90%) 1. m-cpba, (100%) 2. Na, benzene (20%) 3. MsCl andout 08 3/20/98 11:15 AM van Tamelen, JACS 1983, 142

Tanis - Retrosynthetic Analysis Bn Bn Tanis - Cationic Cyclization 1. PhCCl 2. Se 2, TBP (70%) Ac 1. (L) - DIPT, Ti(iPr) 4 TBP (83%, >95%ee) 2. BnBr, Na (88%) 3. Na, (99%) 4. n-buli, TsCl, LiCl (85%) BF 3 Et 2 Et 3 N, -78 C (72%) MgCl LiCuCl 4 (79%) Bn Cl Bn Bn andout 09 3/20/98 11:16 AM Tanis, Chuang, ead JC 1988, 4929 Tanis, Chuang, ead TL 1985, 6147

Tanis - Completion of the Synthesis Bn 1. Swern (97%) 2. MgBr 2, then L-Selectride (95%) Bn Diastereoselection 8.5:1 1. LA (89%) 2. acetone, + (93%) 1. NBS, DMF 2. i. n-buli ii. I (65%) 2 / Pd-C 96% m-cpba 97% McMurry's Intermediate Tanis, Chuang, ead JC 1988, 4929 Tanis, Chuang, ead TL 1985, 6147 Corey - Retrosynthetic Analysis TBS C 2 P(Et) 2 C 2 TBS TBS andout 10 3/20/98 11:17 AM

Corey - Total Synthesis Ac 1. Se 2, Et 2. NaB 4 (61%) Ac 1. TBS-Cl, Et 3 N, DMAP 2. K 2 C 3, (90%, 2 steps) 3. MsCl, Et 3 N 4. LiBr, TF TBS Br (90%, 3 steps) Clg TBS C 2 1. g(ccf 3 ) N 2 2. NaCl, 2 (60%) TBS C 2 P(Et) 2 Na, (Et) 2 PCl TBS C 2 Corey, JACS 1980, 1742 Tius, Ph.D. Thesis, arvard Corey - Elaboration of the Bicycle C 2 1. C 2 C 2, p-ts, Ph (90%) C 2 1. TBAF 2. L-Selectride C 2 Clg 2. NaB 4, DMF, 2 3. PDC, C 2 Cl 2 3. C, p-ts (58%) TBS TBS 1. LA 2. PCC 3. Cl 4 (90%) andout 11 3/20/98 11:19 AM S S TMS C 1. TMSS(C 2 ) 3 STMS ZnI 2, CCl 3 (88%) 2. TMSCN, ZnI 2 (97%) 3. DIBAL- (75%) 1. MVK, DBU, K 2 C 3 TF/ 2. pyrrolidine/ac C Corey, JACS 1980, 1742 Tius, Ph.D. Thesis, arvard

Corey - Construction of the C/D Ring System S S TMS 1. LiSi 3, MPA 2. LDA, MPA, then 2, Ac (64%, 2 steps) S S C C 1. NaB 4 (100%) 2. TBSCl, DMAP Et 3 N 3. IN NI 4. 2, Pd/C 1. TBAF 2. TsCl, DMAP, Et 3 N (70%, 5 steps) 3. LiN() 2, -120 (90%) TBS Corey, JACS 1980, 1742 Tius, Ph.D. Thesis, arvard Corey - Completion of the Synthesis 1. Cl 4 (76%) 2. Li Et 3. Ac, 1:1 Diastereoselection 1. (49%) 2. 1N Cl (74%) Corey, JACS 1980, 1742 Tius, Ph.D. Thesis, arvard andout 12 3/20/98 11:21 AM

Ireland - Retrosynthetic Analysis C 2 TMS TMS N 2 Ireland - Synthesis of 'omo-wieland Mischer Ketone' 1. Na/N 3 (52%) 1. KN 2, then I (100%) 2. Al(i-Pr) 3 2. Li (100%) 1. oxalic acid, 2 (90%) 2. Li/N 3 (85%) 35% 1. C 2 C 2 p-ts (85%) I 2, 130 C 2. 2, hematoporphyrin 2Cl pyr, hv, then Ac 2 (100%) 57:43 52% andout 13 3/20/98 11:23 AM Ireland, JACS, 1981, 2446 Ireland, JC, 1984, 1001 Ireland, JC, 1979, 4323 Ireland, JC, 1979, 4318

Ireland - etero-diels Alder Reaction C 2 Si(C 3 ) 3 R TMS 125 C (69%) DIBAL Ph 3 P=C 2 (95%) R = C 2 R = C R = C=C 2 150 C sealed tube (84%) TMS TMS N 2 1. n-buli, i-amn (85% borsm) 2. N 2 Cl Ireland, JACS, 1981, 2446 Ireland, JC, 1984, 1001 Ireland - the Rearrangement TMS TMS hv, NaC 3, C 3 N 2 TMS E Si 2 (60%) TMS [2 +2] andout 14 3/20/98 11:24 AM Ireland, JACS, 1981, 2446 Ireland, JC, 1984, 1001

Ireland - Further Elaboration 1. DIBAL- (99%) 2. TBSCl, Imid (95%) 1. s 4, pyr 2. DMP, p-ts 3. TBAF, TF (92%) TBS 1. n-buli, TMEDA 2 NPCl 2 2. N 2, Li, (86%) PPTS, acetone (95%) Ireland, JACS, 1981, 2446 Ireland, JC, 1984, 1001 Ireland - Completion of the Synthesis 1. K, TF; TMS-Cl, Et 3 N 2. Pd(Ac) 2 (90%, 2 steps) (C 2 ) x, PhS Et 3 N, Et (78%) PhS Li, N 3, -TF Et 3 N, TMS-Cl, TF (90%) andout 15 3/20/98 11:25 AM L-Selectride, TF, then Cl/ (60%, 2 steps) Li, TF, C TMS Ireland, JACS, 1981, 2446 Ireland, JC, 1984, 1001

Iwata - Retrosynthetic Analysis MM C 2 Iwata - Sucessive Alkylations C 2 C 2 s-bu 1. I, K 2 C 3 (100%) 2. Na, () 2 C 3. Cl, Pd/C (98%) 1. Br/Ac (100%) 2. sec-bubr, DBU (72%) 3. Rh/Al 2 3 (99%) 1. TBSCl, imid (95%) 2. LA (98%) 3. PCC, NaAc (91%) MM 1. Br 2, MPA (85%) 2. TsCl, pyridine (75%) 3. LiBr (98%) 4. K (99%) MM 1. C 2 =CMgBr (83%) 2. MM-Cl, DIEA (77%) 3. B 3 -TF, 2 2 (83%) 4. TBAF (99%) TBS C Iwata, Chem. Pharm. Bull., 1994, 1756 Iwata, Chem. Pharm. Bull., 1995, 193 Iwata, Chem. Pharm. Bull., 1985, 944 Iwata, Chem. Pharm. Bull., 1993, 1900 andout 16 3/20/98 11:26 AM

Iwata - Completion of the Synthesis MM MM MM 1. LDA, TF, then PhSeBr, 2 2, (61%) 2. TP(C 2 ) 4 Cl, Li, 1,2-dibromoethane (98%) 1. PCC (81%) 2. LiCu 2 (67%) TP TP 1. acetone, Cl (97%) 2. Swern (76%) 3. p-ts, Ph, (89%) 1. 3,5-dimethylpyrazole Cr 3 (75%) 2. Pd(PPh 3 ) 4, n-bu 3 P, CN, CN 4 (80%) 1. C 2 C 2, p-ts (75%) 2. LA (96%) 3. Ac 2, DMAP (94%) Ac elaborated to Aphidicolin by the methods of Ireland and Smith Iwata, Chem. Pharm. Bull., 1994, 1756 Iwata, Chem. Pharm. Bull., 1995, 193 Iwata, Chem. Pharm. Bull., 1985, 944 Iwata, Chem. Pharm. Bull., 1993, 1900 Fukumoto - Retrosynthetic Analysis Br andout 17 3/20/98 11:28 AM

Fukumoto - The eck Reaction LDA, TF Bromoacrolein (89%) Br 1. Pd(Ac) 2, P-(o-Tolyl) 3 K 2 C 3, CN, (90%) 2. C 2 C 2, PPTS (89%) 1. C 2 =CEt, g(tfa) 2 2. Toluene,, then NaB 4 (82%) Diastereoselection 3:1 1. 2, PdCl 2, CuCl (70%) 2. 2, Pd-C (82%) 3. Ph 3 P=C 2 (81%) 1. methylene blue, 230 C 2. 2, hv, porphyrin, pyr 3. NaI, Ac 4. Mn 2 (82%) 1. PCC, NaAc (92%) 2. Ph 2 P()C 2 C 2 =C 2 n-buli, MPA Iwata's Intermediate Fukumoto Tet, 11153 1994 Fukumoto, Tet, 10183, 1994 Fukumoto, TL, 6495, 1994 olton - Retrosynthetic Analysis TBS C TBS R TBS Li Tol S TBS S Tol andout 18 3/20/98 11:29 AM

olton - EnantioselectiveTotal Synthesis TBS Li Tol S TBS S Tol Li TBS S Tol Diastereoselection 7.4:1 (75%) 1. Vinyllithium 2. F/ (76%) C TBS 1. PPTS/2-ethoxydioxylane (89%) 2. 3, DMS 3. LA 4. TBS-Cl, DMAP 5. Cr 3, pyridine (65%) R Na/ (100%) S Tol Zn/N 4 Cl (94%) R = S()Tol R = olton, JACS, 1987, 1597 olton - Completion of the Synthesis C TBS 1. KtBu, 0 C 2. 2, Pd/C, NaEt 3. C 2 C 2 PPTS (90%) TBS 1. Li, N 3, C 2 2. L-Selectride TBS C, p-ts, F 85% TBS Corey's Intermediate andout 19 3/20/98 11:31 AM olton, JACS, 1597, 1987

The Final Tally Longest Linear Sequence verall Yield McMurry Trost van Tamelen Bettolo/Lupi Ireland Corey Tanis Iwata Fukumoto olton 18 steps 23 steps 25 steps 24 steps 28 steps 37 steps 27 steps 40 steps 25 steps 28 steps 0.9% yield 0.6% yield 0.03% yield 2.9% yield 0.93% yield 0.96% yield 2% yield 0.19% yield 2.3% yield 1.65% yield andout 20 3/20/98 2:14 PM