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Lecture1 123713A
The document discusses various topics related to chirality and stereochemistry including: - Different forms that can exhibit chirality beyond just tetrahedral stereocenters. - The relationship between enantiomers, diastereomers, and meso compounds for molecules with multiple stereocenters. - How purity of chiral compounds is measured in terms of enantiomeric excess and ratio, and diastereomeric excess and ratio. - Common methods for determining enantiomeric excess such as derivatization reactions and chiral chromatography.
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Lecture1 123713A
- 1. gareth j rowlands ANDTOTAL SYNTHESIS 123.713 A/B STEREOSELECTIVE 1
- 2. why do weneedTotal Synthesis? ©Wsiegmund@wikimedia commons O AcO H OH OBz OH O O OH Ph BzHN AcO O AcO taxol 2
- 3. ©ALTO CONTRASTE .Edgar AVG --BUSY--@flickr AcHN O H2N CO2Et Tamiflu® oseltamivir 3
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- 5. © Armed ForcesPest Management Board@flickr N N Cl N NH O2N Imidacloprid (Advantage®) EUR 597 million 5
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- 7. light-driven molecular motor Me(ax) Me(ax) (3R,3'R)-(P,P)-trans stable Me(eq) Me(eq) (3R,3'R)-(M,M)-trans unstable (3R,3'R)-(M,M)-cis unstable Me(eq) Me(eq) (3R,3'R)-(P,P)-cis stable Me(ax) Me(ax) ≥280 nm ≥ 380 nm ≥ 280 nm ≥ 380 nm 20°C60°C direction of rotation Feringa, Acc. Chem. Res. 2001, 34, 504 7
- 8. nanomotor to moveobjects rotor controls direction anchor Feringa et al., Nature 2006, 440, 163 8
- 9. nanomotor to moveobjects Feringa et al., Nature 2006, 440, 163 x8 real time 9
- 10. nanomotor to moveobjects Feringa et al., Nature 2006, 440, 163 x8 real time 9
- 11. O AcO H OH OBz OH O O OH Ph BzHN AcO O AcO taxol Me(ax) Me(ax) AcHN O H2N CO2Et what propertydo all these molecules share ? 10
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- 13. course structure Lecture 1:introduction Lecture 1: problems Lecture 2: catalysis Lecture 2: problems Lecture 3: retrosynthesis Lecture 3: examples Lecture 4: synthesis Lecture 4: assignment 12
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- 15. Number16|2009 ChemComm Pages2053–2224 FEATURE ARTICLE Toshifumi Dohiand Yasuyuki Kita Hypervalent iodine reagents as a new entrance to organocatalystsISSN 1359-7345 COMMUNICATION Norifumi Fujita, Seiji Shinkai et al. An organogel system can control the stereochemical course of anthracene photodimerization 1359-7345(2009)16;1-0 www.rsc.org/chemcomm Number 16 | 28 April 2009 | Pages 2053–2224 Chemical Communications As featured in: See Debashish Roy, Jennifer N. Cambre and Brent S. Sumerlin, Chem. Commun., 2009, 2106. www.rsc.org/chemcomm Registered Charity Number 207890 By including polymer segments that are sensitive to three different stimuli,“schizophrenic”, triply-responsive block copolymers were obtained. RAFT copolymerization with a boronic acid containing monomer led to block copolymers capable of forming both micelles and reverse micelles, with the self-assembly being governed by the temperature, pH, and sugar concentration of the local environment. Title: Triply-responsive boronic acid block copolymers Showcasing research from Professor Brent Sumerlin’s laboratory, Southern Methodist University, USA. FEATURE ARTICLE Toshifumi Dohi and Yasuyuki Kita Hypervalent iodine reagents as a new entrance to organocataly stsISSN 1359-7345 COMMUNICA TION Norifumi Fujita, Seiji Shinkai et al. An organogel system can control the stereochemic al course of anthracene photodimeri zation 1359-7345(20 09)16;1-0 www.rsc.org /chemcomm Number 16 | 28 April 2009 | Pages 2053–2224 Chemical Communications ume7|Number9|2009 www.rsc.org/obc Volume 7 | Number 9 | 7 May 2009 | Pages 1737–1988 COMMUNICATIONJennifer R. Hiscock et al.Fluorescent carbazolylurea anion receptors 1477-0520(2009)7:9;1-6 D7903 · ASCAF7 · 351 (5) · 661–804 (2009) · ISSN 1615-4150 · No. 5, March 2009 5/2009 ASC 5-Year Impact Factor 2007 5.193 The Cutting Edge that Stays Sharp! Review: Transition Metal-Catalysed, Direct and Site-Selective N1-, C2- or C3-Arylation of the Indole Nucleus: 20 Years of Improvements Lionel Joucla, Laurent Djakovitch journals 14
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- 19. ©DrStarbuck @ Flickr chiralobject non-superposable18
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- 22. OH O HS NH2H HO O SH H2N H a 1:1mixture of enantiomers racemate is called a 21
- 23.
- 24. CH3 HO O H NH214 2 3 naming: priorities groups CH3NH2 H CO2H 1st atom C N H C 2nd atom H, H, H O, O, O priority 3 1 4 2 23
- 25. naming: lowest priority points away CH3 HO O HNH2 H3C OH O HH2N ≡ 14 2 3 1 4 2 3 24
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- 28. been taught is whatyou have O O O O O O O O ©MonkeyBoy69@flickr not entirely true chiral four different groups but does not have 27
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- 30. chiralityof other forms helical P[8]helicene M [8]helicene 29
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- 35. stereocentres3 compounds 8 HO CHO OH OH OH HO CHO OH OH OH HO CHO OHOH OH HO CHO OH OH OH HO CHO OH OH OH HO CHO OH OH OH HO CHO OH OH OH HO CHO OH OH OH 34
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- 45. properties differenthave diastereoisomers NH2 NH2 mp =41-45°C bp = 221°C NH2 NH2 44
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- 47. ©brittanyculver@flickr how do wemeasure purity? 46
- 48. NH2 NH2 NH2 H2N NH2 NH2 = 80% 20% 60%ee enantiomericexcess (ee) 47
- 49. NH2 NH2 NH2 H2N = 80% 20% 4 :1 enantiomeric ratio (er) 80 : 20 48
- 50. NH2 NH2 NH2 NH2 80% 20% diastereoisomeric excess60% de diastereoisomeric ratio 4 : 1 dr diastereoisomeric ratio 80 : 20 dr 49
- 51. ©brittanyculver@flickr how do wemeasure ee? 50
- 52.
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- 54. samethe ©David Reeves fromFlickr chemistry diastereoisomers need 53
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- 56. OH Ph CO2H DCC, DMAPOMeF3C iPr OH O Ph F3C OMe iPr O H O Ph F3C OMe covalent Mosher’s acid 73JACS512, 73JOC2143 & 91JACS4092 derivatisation 55
- 57. HO2C CO2H OTol OTol O2C CO2H OTol OTol S diastereoisomer isinsoluble NaOH (–)-propranolol β-blocker O OH NH O OH NH2 O OH NH ionic (salt) derivatisation 56
- 58. ©Pere Tubert Juhé@flickr temporary interactions chiral chromatography Si N H O NO2 NO2 Si OSi SiO O O O OSi OSi O O O O O Me Me silica chiral amine 57
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- 60. 7 = 97.5 2.5 95%: eree δ𝚫G‡ = 8.3 kJ mol-1 at 0°C 59
- 61. one substituent CH3 CH3 H CH3 H 95% equatorial more stableby 8 kJmol–1 5% axial disfavoured 60
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- 63. H3C H Ph O H Et ...although oneconformation of a molecule is more stable than other possible conformations, this does not mean that the molecule is compelled to react a s i f i t w e r e i n t h i s conformation or that it is rigidly fixed in any way. “ ..” D.H.R. Barton, Experientia 1950, 6, 316 62