1. Clark W. Still Career in Review
Department of Chemistry, University of Ottawa
March 17th, 2009
By Anik Michelle Chartrand

2. Who Is He ? 1946 - Born in Augusta, Georgia
Graduated from Winter Haven High
School in Polk Country, FL
1969- B.Sc. At Emory University
1972- Ph.D. At Emory University – Advisor was David Goldsmith
1973- Postdoc at Princeton University (computer related)
1974/75- Postdoc at Columbia University with Gilbert Stork
1975/76- Professor at Vanderbilt University in Nashville, TN
1977 to 98 - Professor at Columbia University in NY, NY
1999 – Professor Emeritus, Columbia University in NY, N

3. Graduate Studies

4. His Graduate Work (1969-72) Diborane Reductions of Oxygen Heterocycles
Hydroboration-Oxydation Products of Oxygen Heterocycles
Maybe add example
W. C. Still and D.J. Goldsmith, J. Org. Chem., 1970, 35 (7), 2282

5. His Graduate Work ( )
The decarboxylative elimination reaction of β,γ- epoxyacids
to make allylic alcohols
Bicyclic Intermediate for Trichothecane Synthesis
Exploitation of an Enolate as a Protecting Group
Tandem sequence involving bis alkylation
Still, W.C.; Lewis, A.J.; Goldsmith D.; Tetrahedron Letters, 1971, 18, 1421
Still, W.C.; Lewis, A.J.; Goldsmith D.; Tetrahedron Letters, 1973, 48, 4807

6. His Graduate Work ( )
Most of his work with Prof. Stork concentrated of the formation of Gibberellic Acids B-C-D ring:
Reductive cyclization of Ethynyl ketones
Add reference for second part.
Unusual regiospecificity in the enolization of a ketone as the result of a difference
in energy to achieve the best overlap of an alpha hydrogen
Stork, G.; Boeckman, R.K. Jr..; Taber, D.F.; Still W.C. Singh, J. ,JACS, 1979, 101 (23) 7107
Stork, G.; Still W.C. Singh, J., Tetrahedron Letters, 1979, 52, 5077

7. Independent Researcher
Vanderbilt University
Columbia University

8. His Work at Vanderbilt University (1975-76)
Organo cuprates and the development of a new highly selective stereoselective alkylation agent to produce axial alcohols
“ In contrast to the numerous highly stereoselective reducing agents which have
been developed, the ability of reagents for the addition of unhindered alkyl
nucleophiles to ketones with high stereoselectivity is limited.”
Conjugate Addition of trimetylsilyllithium – Axial addition is highly favoured
Macdonald, T.L.; Still, W.C.; JACS, 1975, 97(18), 5280 & Still, W.C., J. Org. Chem., 1976, 41(18), 3063

9. His Work at Vanderbilt University (1975-76)
Allyloxy Carbanions:
Cyclization to vinyl oxetans via allyloxycarbanions :
Selective fomation of the more strained oxetane as long
as the addition produces the cis ring juncture
-First example od allyloxycarbanion cyclisation.
High regio and stereoselectivity
- one of the first examples of the nonphotochemical oxetane synthesis.
Still C.W., Tetrahedron Letters, 1976, 25, & Still, W.C.; Macdonald, T.L.; J. Org. Chem., 1976, 41(22), 3620.

10. His Work at Vanderbilt University (1975-76)
Claisen Variant:
Read paper for claisen variant.
Add diagrams for tin.
At the time most carbon carbon bond formations were done via a carbonyl group behaving like a hydroxyl0substituted carbocation, but there was almost no examples of the oposite charge affinity pattern because there was alack of regent availability to do so.
- Still envisionned that a general preparation of a masked carbinyl carbanion would be the best way to proceed and so he divised a a way to make it via a alpha-alkoxy organostannane.
- he found that generating Bu3SNLI was eisier with tributyltin hydride and LDA than with hexabutyl ditin with n-buli or MeLi.
- One problem he had envisioned was that anion-destabilizing alkyl substituents R might be expected to bias the equilibrium between SnBu3 and Li. But they report that both alkyl and aryl substituted alpha-alkoxy organolithium reagents produce the desired product in high yields.
Ask for equilibrium explanation.
Tin chemistry (stannylation/destannylation)
α-Alkoxy Organolithium Reagents
Still, C.W.; Schneider, M.J., JACS, 1977, 99(3), 948 & Still, C.W., JACS, 1978, 100 (5), 1481

11. His Work at Vanderbilt University (1975-76)
Tri-alkyl tin anions undergo high yield conjugate addition to α,β-enones to give
the regiospecific enolate 42 40 41
Alkylstannanes are smoothly oxidized by chromic anhydride/pyridine to the
corresponding ketone
Alkylation and oxidation – efficient dialkylative enone transposition
Still, C.W., JACS, 1977, 99(14), 4836

12. Columbia University (1977-1998)
Anionic [2,3]-sigmatropic rearrangements
Still developped a highly efficient way to synthesize stereoselectively a C18 Cepcropia hormone. Here i will demonstrate how he got the to core of the molecule. Synthesis of X tool 3 steps. From that he was able to do a 2, 3 sigmatroips RR to give the selective Z-homoallylic alcohol product X.
The stereoselctivity comes from the transition state that has the speudo axial R group, minimizing the strain and giving the trans product as opposed to the cis product.
Here they report a efficient [2,3]-sigmatropic Wittig rearrangement which produces 2-trisubstituted homoallylic
alcohols in high yields and with >95% stereoselectivity. This reaction is the first example of a
[2,3]-sigmatropic rearrangement having a transition state which prefers pseudoaxial substitution
Still, C.W.; McDonald J.H. III; Collum, D.B.; Mitra, A., Tetrahedron Letters, 1979, 7, 593 &
Still, C.W.; Kahn, M.; Mitra, A., J. Org. Chem., 1978, 43(14), 2923

13. Columbia University (1977-1998)
Rapid Chromatographic Technique for Preparative Separation of
moderate resolution
“ We have recently developed a substantially faster technique
for the routine purification of a products which we call
flash chromatography.”
Monensin – Polyether antibiotic and naturally occurring ionophore
17 asymmmetric centers, 26 carbon backbone
Theoretically stereoisomers can exist
1) Still, C.W.; Kahn, M.; Mitra, A., J. Org. Chem., 1978, 43(14), ) Still, W. C.; Dongwei, J. Org. Chem., 1988, 53, ) Still, W.C.; MacDonald, J.H.III; Collum, D.B.; JACS, 1980, 102(6), ) Still, W.C.; MacDonald, J.H.III; Collum, D.B.; JACS, 1980, 102(6), )Still, W.C.; MacDonald, J.H.III; Collum, D.B.; JACS, 1980, 102(6), 2120

14. Columbia University (1977-1998)
Direct Synthesis of Z-unsaturated esters; a useful modification of the
Horner-Emmons Olefination
Horner-Wadsworth-Emmons
Amongs his many total syntheses of natural products one of his most famous was that of Periplanone –B. His work on macrocyclo conformation and reactivity was one of the key concepts demonstrated in the synthesis. For example he demonstrated that the peripheral attack of the double bond would be favores because the anti-periferal attack is shielded by the ring. To elucidate the structure and determine the relative stereochemistry of periplanone –B he synthesiszed 3 of the 4 stereoisomers of this natural product.
Still – Gennari Modification
Still, W.C., JACS, 1979, 101(9), 2493 & Adams, M.A.; Nakanishi, K.; Still, W.C.; Arnold, E.V.; Clardy, J.; Persoons, C.J.; JACS, 1979, 101(9), 2495

15. Z-trisubstituted Allylic Alcohols via the Wittig Reaction
Schlosser, M; Christmann, K.F. Angew. Chem. Intl, Ed., 1966, 5(1), 126 &
Schlosser, M; Christmann, K.F,; Muller, G., Angew. Chem. Intl, Ed., 1966, 5 (17), 667 &
Corey, E.J.; Yamamoto, H.; JACS, 1970, 92(1), 226

16. Z-trisubstituted Allylic Alcohols via the Wittig Reaction
No β-oxido Ylide intermediate or n-BuLi required α
Counterion effect
Phosphonium fluoroborate Vs
Phosphonium halide
α ‘
In general substitution at the alpha position of the ketone tends to improve the stereoselectivity and at he alpha’ it tends to diminish it.
Chemical yield are very high provided that the atoms being joined are relatively unhindered.
- The ylide may be substituted by various alkyl chains so long as the carbon beta to the phosphorous is not branched.
α-santalol
Sreekumar, C.; Darst, K.P.; Still, W.C., J. Org. Chem, 1980, 45(21), 4260

17. Columbia University (1977-1998)
Dichlorocarbene cyclopropanation of allylic alcohols:
This is a Simmons-Smith
equivalent that works
well in acyclic systems
Synthesis of Alternating Hydroxy- and Methyl-Substituted Hydrocarbons by
Oxymercuration of Cyclopropylcarbinols.
Mohamadi, F.; Still, W.C., Tetrahedron Letters, 1986, 27(8), 893 &
Collum, D.B.; Still, W.C., Mohamadi, F., JACS, 1986, 108(8), 2094

18. Columbia University (1977-1998)
A highly stereoselective synthesis of trans epoxides via arsonium Ylides
High stereoselectivity
for trans epoxide ≥ 50:1
Remote 1,3-, 1,4-,and 1,5- asymmetric induction. A stereoselective approach to acyclic
diols via Cyclic Hydroboration
Still, W.C.; Novack, V. J., JACS, 1981, 103(5), 1283 &
Still , W.C..; Darst, K.P., JACS, 1980, 1021(24), 7385

19. Columbia University (1977-1998)
Synthesis of Macrocyclic Trichothecanoids: Baccharin B5 and Roridin E 85 86 87 88
Chemical consequence of conformation in macrocyclic compounds. An effective approach
to remote asymmetric induction.
Still, W.C.; Gennari, C.; Noguez, J.A..; Pearson, D.A., JACS, 1984, 106(1), 260 &
Still, W.C.; Galynker, I., Tetrahedron, 1981, 37 (23), 3981

20. Macrocycles
Stereochemical control - acyclic and macrocyclic natural products rely on some form of
absolute stereochemical control to set up remote diastereometric relationship
Readily available enantiomerically pure S.M.
Resolution of an intermediate
Asymetric induction by enantiomerically pure reagent
Still’s alternative – pre-existing substrate chirality, which may be quite distant from the
reaction site, to direct the stereoselectivity of the reaction.
Conformations – Transannular non bonded repulsions and high-energy torsional
arrangements must be minimized
Still, W.C.; Galynker, I., Tetrahedron, 1981, 37(23), 3981

21. 8-Membered Ring

22. 9-Membered Rings
Still, W.C.; Galynker, I., Tetrahedron, 1981, 37 (23), 3981

23. Peripheral vs Antiperipheral Attack
3D Structure – sp2 centers are perpendicular to the plane of the ring
Cis-cyclohexene
Cis- cyclooctene
Cis- cyclodecene
2 faces of π-system are sterically different
Peripheral attack preferred
Still, W.C.; Galynker, I., Tetrahedron, 1981, 37 (23), 3981

24. Periplanone B- Total synthesis and structure of the Sex Excitant Pheromone of the American Cockroach
Female species of Periplaneta americana, the American
Cockroach.
In the early 70’s Persoons et al. Isolated two extremely active compounds, periplanones-A (-20 pg) and -B (-200 pg).
Periplanone-B was characterized spectrally and
tentatively assigned a germacranoid structure.
Still reported highly stereoselective syntheses of three of the four possible diastereomers.
Still, W.C., JACS, 1979, 101(9), 2493

25. Periplanone B – First Diastereomer
Except for the geometries of the endocyclic epoxide and
olefin (cis and trans, respectively) the relative stereochemistry
in periplanone-B was unknown. Therefore a flexible route to
i had to be developed which allowed for the stereochemical
uncertainties at C-1, C-2, and C-8. The basic plan called for
the preparation of an advanced cyclodecanoid intermediat which could be converted in a stereorational fashion to each
possible diastereomer of i for spectral and biological evaluation.
C-5 and C-6 Diaxial coupling (10Hz);
C-7 and C-8 trans coupling (16 Hz)
Still, W.C., JACS, 1979, 101(9), 2493 &
Adams, M.A.; Nakanishi, K.; Still, W.C.;
Arnold, E.V.; Clardy, J.; Persoons, C.J.; JACS, 1979, 101(9), 2495

26. Periplanone B – Stereocontrol ApproachX
Peripheral
Attack
Diastereomers synthesis:
1-5 Cyclodecadienes have a well defined conformation
Olefinic linkage perpendicular to plane of ring.
Attack from less hindered peripheral face of the π system
Still, W.C., JACS, 1979, 101(9), 2493 &
Adams, M.A.; Nakanishi, K.; Still, W.C.; Arnold, E.V.; Clardy, J.; Persoons, C.J.; JACS, 1979, 101(9), 2495

27. Periplanone B – First Diastereomer
Corey-Chaykovsky epoxidation.
The Corey–Chaykovsky reagent, dimethylsulfonium methylide
1, generated from a trimethylsulfonium salt and a base is known
to react with an aldehyde or a ketone to give an epoxide by
an overall methylene insertion.1 Excess reagent could lead to
the formation of allylic alcohol by further addition of the
ylide on the epoxide.2
Spectral comparison with
authentic Periplanone-B
concludes they are
Unidentical

28. Periplanone B – First Diastereomer
First Disatereomer
300-MHz NMR strongly suggest :
Only difference is the configuration of the isopropyl group.
Pseudo-axial in X: (J7-8 = 5, J8-9a = 7.5, J8-9b= 2 Hz)
Pseudo-equatorial (Periplanone B) : (J7-8 = 10, J8-9a = 10, J8-9b= 5.5 Hz
Still, W.C., JACS, 1979, 101(9), 2493 &
Adams, M.A.; Nakanishi, K.; Still, W.C.; Arnold, E.V.; Clardy, J.; Persoons, C.J.; JACS, 1979, 101(9), 2495

29. Periplanone B – Second Diastereomer
Peterson-Chan olefination and epoxidation didn’t work. The latter was a problem because the double bond 6-7 was more reactive.
NMR of 116 is very different than Periplanone B
Transannular -O- interaction is replaced by a more severe -CH2- interaction
Still, W.C., JACS, 1979, 101(9), 2493 &
Adams, M.A.; Nakanishi, K.; Still, W.C.; Arnold, E.V.; Clardy, J.; Persoons, C.J.; JACS, 1979, 101(9), 2495

30. Periplanone B -Third Diastereomer
Construction of the stereoisomeric C-2 – C-3 cis epoxide:
Desired epoxide is the more hindered one.
Disfavoured
Antiperipheral attack
needed
favoured
peripheral attack
NOT WANTED
Alternate tactic was chosen – construction of the C-5 – C-7 conjugated diene :
New conformation exposes opposite face to peripheral attack
Still, W.C., JACS, 1979, 101(9), 2493 &
Adams, M.A.; Nakanishi, K.; Still, W.C.; Arnold, E.V.; Clardy, J.; Persoons, C.J.; JACS, 1979, 101(9), 2495

31. Periplanone B -Third Diastereomer
Comparison of (±) – 121 with Periplanone–B showed they were identical
Still, W.C., JACS, 1979, 101(9), 2493 &
Adams, M.A.; Nakanishi, K.; Still, W.C.; Arnold, E.V.; Clardy, J.; Persoons, C.J.; JACS, 1979, 101(9), 2495

32. Columbia University (1977-1998)
An internal Coordinate Monte Carlo method for searching conformational Space
Random Search for finding the low-energy
conformations of molecules
Was the first to create a software available and
and fairly easy to use for the general public
Chang, G.; Guida, W.C.; Still, W.C., JACS, 1989, 111 (8), 3075

33. Columbia University (1977-1998)
Complex Synthetic chemical libraries indexed with molecular tags
A new generation of Fluorescent chemosensors demonstrate improved analyte detection
sensitivity and photobleaching resistance.
Nestler, H.P.; Barlett, P.A.; Still, W.C., J. Org. Chem., 1994, 59(17), 4723 &
Ohlmeyer, M.H.J.; Swanson, R.N.; Dillard, L.W.; Reader, J.C.;Asouline, G.;Kobayashi, R.; Wigler, M.;Still, W.C., Proc. Natl. Acad. Sci. USA,
1993, 90(23), & Rothman, J.H.; Still, W.C., Bioorg.& Med. Chem. Letters, 1999, 9(4), 509 &
Chen, C.T.; Wagner, H.; Still, W.C., Science, 1998, 279 (5352), 851

34. Complex Synthetic Chemical Libraries Indexed with Molecular Tags
Spacially segrated arrays
Only small libraries
Multivalent synthesis methods
Moderate complexity library is produced
Pooling of multiple reagents during synthesis
Pool is identified to have interesting properties
Resynthesized with lower and lower complexity till one compound is identified
NOT practical for construction of massive libraries.
Split synthesis
On solid particles (ex. Beads)
Each bead has a product from a single reaction sequence bound to it
Selection of a bead with desirable property followed by ID of substrate by analytic method.
Only for compounds that can be readily elucidated by micro scale sequencing.
Co-synthesis method
Co-synthesis of a sequencable tag encoding the steps and reagents used in each step.
Oligonucleotide and oligopeptide tags are used
Problem = tag is labile, can associate selectively with biological receptors.
Ohlmeyer, M.H.J.; Swanson, R.N.; Dillard, L.W.; Reader, J.C.;Asouline, G.;Kobayashi, R.; Wigler, M.;Still, W.C., Proc. Natl. Acad. Sci. USA, 1993, 90(23), 10922

35. Complex Synthetic chemical libraries indexed with molecular tags
Chemically encoded combinatorial library
Synthesis on microsphere beads (like in split method)
Each step tagging molecules are attached to the beads
Encodes both the step number and reagent used in that step = Binary record
No co-synthesis required (tags not connected)
20 tags = different syntheses
Ohlmeyer, M.H.J.; Swanson, R.N.; Dillard, L.W.; Reader, J.C.;Asouline, G.;Kobayashi, R.; Wigler, M.;Still, W.C., Proc. Natl. Acad. Sci. USA,
1993, 90(23), 10922

36. Result Analysis Peptide library beads stained with mAb 9E10.
GC of tags from EQKLISEEDLGGGG-Bead
Ohlmeyer, M.H.J.; Swanson, R.N.; Dillard, L.W.; Reader, J.C.;Asouline, G.;Kobayashi, R.; Wigler, M.;Still, W.C., Proc. Natl. Acad. Sci. USA,
1993, 90(23), 10922

37. General Method for Molecular Tagging of Encoded Combinatorial Libraries
Requires no particular tag-attaching functional group other than what already
makes up the polymer matrix
New tagging reagent = tag plus linker
Nestler, H.P.; Barlett, P.A.; Still, W.C., J. Org. Chem., 1994, 59(17), 4723

38. Fluorescent, Sequence-Selective Peptide Detection by Synthetic Small molecules
Chemosensors are small molecules that signal the presence of analytes, and typically have
two components:
Receptor – site that selectively binds an analyte
Redout mechanism – signals binding.
Chemosensor for tripeptides in CHCl3.
Function as synthetic analogs of the
antigen-binding site of immunoglobulins
FET signal transduction system
Rothman, J.H.; Still, W.C., Bioorg.& Med. Chem. Letters, 1999, 9(4), 509 &
Chen, C.T.; Wagner, H.; Still, W.C., Science, 1998, ), 851

39. Chemosensors Chemosensor A Chemosensor B Q = COC6H4N=NC6H4NMe2
F = (CH2)2NH-SO2C10H6NMe2
Dabcyl N-hydrosuccinamide ester
Dansyl sulfonamide of ethanolamine

40. Fluorescent, Sequence-Selective Peptide Detection by Synthetic Small molecules
Fluorescence spectra of chemosensor A and B with Peptides P1 and P2
Demonstrate the sequence selective optical detection of peptides
By small molecules chemosensor
Can be extended to solid state libraries
Rothman, J.H.; Still, W.C., Bioorg.& Med. Chem. Letters, 1999, 9(4), 509 &
Chen, C.T.; Wagner, H.; Still, W.C., Science, 1998, 279 (5352), 851

41. New Fluorencent Chemosensors with Improved Photobleaching Resistance
Photobleaching : is the photochemical destruction of a fluorophore.
Major problem with chemosensors that report binding via fluorescence trough UV
This binding interaction induces a change in distance between a fluorophonre attached to one of the macrocyclic arms and a quenching moiety attached to the core. The are engaged in a Forster typer interation. (FRET – fluorescence resonance energy transfer_)
FRET ( fluorescence resonance energy transfer) interaction
The level of fluorescence that escapes quenching is proportional
to the binding strength
Photobleaching is a significant source of detection error.
Rothman, J.H.; Still, W.C., Bioorg.& Med. Chem. Letters, 1999, 9(4), 509 &
Chen, C.T.; Wagner, H.; Still, W.C., Science, 1998, 279 (5352), 851

42. New Fluorencent Chemosensors with Improved Photobleaching Resistance
Dansyl fluorofore moiety
Known to undergo photobleaching
Rothman, J.H.; Still, W.C., Bioorg.& Med. Chem. Letters, 1999, 9(4), 509 &
Chen, C.T.; Wagner, H.; Still, W.C., Science, 1998, 279 (5352), 851

43. Dansyl vs Acridone Moiety
Replacement of the dansyl fluorophore moiety with an acridone derivative
Rothman, J.H.; Still, W.C., Bioorg.& Med. Chem. Letters, 1999, 9(4), 509 &
Chen, C.T.; Wagner, H.; Still, W.C., Science, 1998, 279 (5352), 851

44. New Fluorencent Chemosensors with Improved Photobleaching Resistance
Receptor binding saturation experiment.
Receptor is now more resistant to fluorophore photobleaching.
No significant change in binding saturation characteristics
Acridone exhibits increased fluorescence upon binding
Rothman, J.H.; Still, W.C., Bioorg.& Med. Chem. Letters, 1999, 9(4), 509 &
Chen, C.T.; Wagner, H.; Still, W.C., Science, 1998, 279 (5352), 851

45. Conclusion Still was clearly ahead of his time
- Total synthesis - Methodology
- Computational chemistry - Chemical biology etc..
3 most cited papers (from a total of 190 publications):
1) Still W.C.; Kahn M., Mitra A., Rapid Chromatographic Technique for Preparative
Separations with Moderate Resolutions, J. Org. Chem., 1978, 43(14), 2923
Times Cited: 7419
2) Mohamadi F.; Richards N.G.J; Guida W.C.; Still, W.C., Macromodel -an Intergrated
Software System for Modeling Organic and bioorganic Molecules Using Molecular
Mechanics, J. Comp. Chem., 1990, 11(4), 440
Times Cited: 2788
3) Still, W.C.; Tempczyka, A.; Hawley R.C. Semianalytical Treatment of Solvation for
Molecular Mechanics and Dynamics, JACS, 1991, 112(16), 6127
Times Cited: 1511
Retired at 53 years old – Emeritus professor at Columbia University
Never got an NIH grant
Now building planes as a hobby.....

46. Prof. Louis Barriault Graduate students Jason Poulin Minaruzaman
Kassandra Lepack
Francis Barabé
Christiane Grisé-Bard
Eric Beaulieu (Past)
Marie-Christine Brochu (Past)
Steve Arns (Past)
Undergrads
Anne-Catherine Bédard
Grabriel Bellavance
Jean-Francois Vincent-Rocan
Olivier Gagné
Patrick Lévesque (Past)

47. Monensine 17 asymmmetric centers, 26 carbon backbone
theoretically stereoisomers can exist
Polyether antibiotics constitute a growing class of naturally occurring ionophores.
Collum, D.B.; McDonald, J.H. III; Still, W. C., JACS, 1980, 102(2), 2117

48. Retrosynthetic Pathway
Collum, D.B.; McDonald, J.H. III; Still, W. C., JACS, 1980, 102(2), 2117

49. Monensin- Chromic Acid Degradation
Why degradation ? :
Called relay synthesis
Structure proof of advanced synthetic intermediates
Ex: Stereochemistry
Dongwei, C.;Still, W.C.; J.Org. Chem., 1988, 53, 4641

50. Monensin – Further Degradation
Collum, D.B.; McDonald, J.H. III; Still, W. C., JACS, 1980, 102(2), 2117

51. Monensin- Retrosynthetic Scheme
Collum, D.B.; McDonald, J.H. III; Still, W. C., JACS, 1980, 102(2), 2117

52. Monensin- Further Degradation
Collum, D.B.; McDonald, J.H. III; Still, W. C., JACS, 1980, 102(2), 2117

53. Monensin- Further Degradation
Collum, D.B.; McDonald, J.H. III; Still, W. C., JACS, 1980, 102(2), 2117

54. Monensin- Retrosynthetic Scheme
Collum, D.B.; McDonald, J.H. III; Still, W. C., JACS, 1980, 102(2), 2117

55. Forward Synthesis Collum, D.B.; McDonald, J.H.III;
Still, W.C., JACS, 1980, 102(6), 2118

56. Forward Synthesis
Collum, D.B.; McDonald, J.H.III; Still, W.C., JACS, 1980, 102(6), 2118

57. Forward Synthesis
Collum, D.B.; McDonald, J.H.III; Still, W.C., JACS, 1980, 102(6), 2118

58. Forward Synthesis
Collum, D.B.; McDonald, J.H.III; Still, W.C., JACS, 1980, 102(6), 2120