Stereoselective Organic Synthesis
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1 Stereoselective rganic Synthesis Prabhat Arya Professor and Leader, Chemical Biology Program Dean, Academic Affairs, Institute of Life Sciences (An Associate Institute of University of yderabad Supported by Dr. Reddy s) University of yderabad Campus Gachibowli, yderabad , India Adjunct Professor, Biochemistry, McGill University mber, ttawa Institute of Systems Biology tel: (+91) (40) e mail: prabhata@ilsresearch.org website: 1
2 Day 4 Stereoselective Nucleophilic Addition to Carbonyl Group and Enantioselective xidation 2
3 utline Nucleophilic addition to carbonyl group Cram, Felkin-Anh, chelation and dipolar models 1,2 Asymmetric induction in carbonyl addition 1,3 Asymmetric induction in carbonyl addition enantieoselective carbonyl reduction (Masamune, Corey) Diastereoselective oxidation Enantioselective oxidation (Sharpless and Jacobsen) Enantioselective synthesis examples 3
4 Examples of Stereoselective Nucleophilic Addition to Carbonyl Group KB 4 C C Use models here t-buli, Et 2 1,2 Asymmetric Induction -50 o C LA 4
5 Cram s Rule 1,2 Asymmetric Induction Use models here Cram s Rule: J Am Chem Soc 5828 (1952) 5
6 The Cyclic Model for 1,2 Asymmetric Induction S L S L S L R M R Nu R chelation Nu Ph Ph R R Ph Use models here 1,2 Asymmetric Induction J Am Chem Soc, 2748 (1959) 6
7 The Dipolar Model (Cornforth s Model) 1,2 Asymmetric Induction Use models here J Chem Soc, 112 (1959) 7
8 Cram Model Felkin-Anh Model 1,2 Asymmetric Induction favored disfavored Use models here 8
9 1,2 Asymmetric Induction 9
10 1,2 Asymmetric Induction See: Tetrahedron Letts 2205 (1968); J Am Chem Soc, 1124 (1969) and Topics in Curr Chem, 146 (1980) 10
11 Use models here Felkin Anh Products 1,2 Asymmetric Induction Taken from Book: Classics in Stereoselective Synthesis, Chapter 2 11
12 1,2 Asymmetric Induction Felkin Anh Like Use models here Taken from Book: Classics in Stereoselective Synthesis, Chapter 2 12
13 1,2 Asymmetric Induction Taken from Book: Classics in Stereoselective Synthesis, Chapter 2 13
14 1,2 Asymmetric Induction: Diastereoselective Allylation with Chiral Boron Reagents 14
15 Use models here Taken from Book: Classics in Stereoselective Synthesis, Chapter 5 15
16 1,2 Asymmetric Induction: Diastereoselective Allylation with Chiral Boron Reagents 16
17 Enantioselective rganoborane Approach to Carbon-Carbon Bond Formation Roush et al, J Am Chem Soc 8186 (1985) 17
18 Stereoelectronic Effect Use models here Roush et al, J Am Chem Soc 8186 (1985)
19 Use models here Taken from Book: Classics in Stereoselective Synthesis, Chapter 5 19
20 Use models here Taken from Book: Classics in Stereoselective Synthesis, Chapter 5 20
21 R
22 Favored Transition State Disfavored Transition State 22
23 Derived from (+) pinene Use models here Taken from Book: Classics in Stereoselective Synthesis, Chapter 5 23
24 Derived from (+) pinene Use models here Taken from Book: Classics in Stereoselective Synthesis, Chapter 5 24
25 Favored Transition State Disfavored Transition State Si phase attack Re phase attack 25
26 Favored Transition State Disfavored Transition State Si phase attack Bz B Bz B Re phase attack Bz favored Bz Use models here 26
27 Disfavored Transition State Favored Transition State Si phase attack Bz B Bz B Re phase attack Felkin anti Felkin Bz Bz Use models here favored 27
28 1,3 Asymmetric Induction: Stereogenic Centre β to the Carbonyl Group 28
29 1,3 anti Use models here Taken from Book: Classics in Stereoselective Synthesis, Chapter 2 29
30 Use models here Nu -P a -P R 1 2,3 anti P- Nu R 1 Felkin control Nu R 1 1,2 syn and 2,3 anti -P R 1 2,3 syn R 1 M P chelation control -P Nu R 1 1,2 anti and 2,3 syn Taken from Book: Classics in Stereoselective Synthesis, Chapter 2 30
31 Nu Taken from Book: Classics in Stereoselective Synthesis, Chapter 2 31
32 Regents-based Alteration in 1,3 Asymmetric Induction Use models here Nu Taken from Book: Classics in Stereoselective Synthesis, Chapter 2 32
33 Regents-based Alteration in 1,3 Asymmetric Induction External hydride delivery Internal hydride delivery Use models here Taken from Book: Classics in Stereoselective Synthesis, Chapter 2 33
34 Enantioselective Reducing Agents 34
35 R R B B B (1) S 3 (2) -20 o C (3) R 1 N 2 syn coordination boron and small group B S (small) R 1 (large) B S B (small) (small) + B B R 1 (large) R 1 (large) 2 N Use models here S Masmune, J Am Chem Soc, 4551 (1985) and 7402 (1986) 35
36 Catalytic Chiral Reducing Agent Use models here 36
37 The Proposed Catalytic Cycle R Ph + A N Ph Ph B Ph 0.1 eq A, 1.0eqB 3,TF R Ph Ph Ph Ph B B 3 N N + Ph B 2 - B 3 B B 3 R L R S Ph N B - B R L R S Use models here R L R S Ph Ph B N 2 B R S R L E J Corey et al J Am Chem Soc, 5551 (1987) and covered in review article by David Evans et al in Science, vol 240, 420 (1988) 37
38 An Enantioselective Synthesis α Amino Acids Ph N B Ph R CCl 3 nbu B - R CCl 3 N 3 - Cl R - Cl N Cl - + R 3 N C - 2 N 3 3 N - R C - Pd-C R C N 3 R +Cl - CCl Corey et al, J Am Chem Soc, 1906 (1992) 38
39 Enantioselective xidation 39
40 Simple xidizing Agents DMS-DCC xidation N C N S + S R1 R 1 R 2 N C S R N R 2 C C S C 2 R 2 N N R1 + S 2 C R 2 N C N R 1 R 2 + S DMS-xalyl Chloride xidation (Swern) 40
41 xidation of C=C Bond R R + Mn 4 R R Mn R R +Mn 2 R R Mn R R catalytic R N + s R 4 s + R 3 N + R + 2 R + - s 41
42 exo exo endo dr endo dr Taken from Book: Classics in Stereoselective Synthesis, Chapter 9 42
43 Murray Approach Taken from Book: Classics in Stereoselective Synthesis, Chapter 9 43
44 Still Approach Taken from Book: Classics in Stereoselective Synthesis, Chapter 9 44
45 Directing Groups Taken from Book: Classics in Stereoselective Synthesis, Chapter 9 45
46 Directing Groups Taken from Book: Classics in Stereoselective Synthesis, Chapter 9 46
47 Directing Groups Taken from Book: Classics in Stereoselective Synthesis, Chapter 9 47
48 Directing Groups Taken from Book: Classics in Stereoselective Synthesis, Chapter 9 48
49 Application to Lasacolid Synthesis Taken from Book: Classics in Stereoselective Synthesis, Chapter 9 49
50 Enantioselective Sharpless Epoxidation [] from top R R R 3 R 2 R 1 R R Use models here R 2 R 3 R 1 R 3 R 2 R 1 [] from bottom R 3 R 2 R 1 EtC CEt or R, R S, S EtC L-tartrate D- tartrate CEt R R Ti R R R: i-c C 2 Cl 2, -20 o C L-tartrate D-tartrate attack from the bottom face attack from the top face 50
51 51
52 The Proposed chanism Use models here Approach from behind
53 Application to Venustatriol Synthesis D-(-) DET Sharpless Conditions >90%ee CN Br CN Taken from Book: Classics in Stereoselective Synthesis, Chapter 9 53
54 Jacobson Epoxidation 54
55 N N Mn Use models here tbu Cl tbu tbu 4mol% tbu NaCl 84% Ph 92% ee tbu N N Mn tbu tbu tbu Taken from Book: Classics in Stereoselective Synthesis, Chapter 9 55
56 Enantioselective Synthesis of BRL N N Mn C 2 F 5 tbu Cl tbu tbu 4mol% tbu NaCl C 2 F 5 75% 94% ee KtBu N C 2 F 5 N BRL Taken from Book: Classics in Stereoselective Synthesis, Chapter 9 56
57 Enantioselective Synthesis of Indinavir tbu N N Mn Cl tbu tbu 3mol% tbu NaCl 71% 84-86% ee N 2 N N Taken from Book: Classics in Stereoselective Synthesis, Chapter 9 N N CNtBu Ph N 57
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