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Clark W. Still Career in Review. Department of Chemistry, University of Ottawa March 17 th , 2009 By Anik Michelle Chartrand. Who Is He ?. 1946 - B orn in Augusta, Georgia 1964 - Graduated from Winter Haven High School in Polk Country, FL 1969- B.Sc. At Emory University

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Clark W. Still

Career in Review

Department of Chemistry, University of Ottawa

March 17th, 2009

By Anik Michelle Chartrand


Who is he
Who Is He ?

  • 1946 - Born in Augusta, Georgia

  • 1964 - 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



His graduate work 1969 72
His Graduate Work (1969-72)

  • Diborane Reductions of Oxygen Heterocycles

  • Hydroboration-Oxydation Products of Oxygen Heterocycles

W. C. Still and D.J. Goldsmith, J. Org. Chem., 1970, 35 (7), 2282


His graduate work 1969 721
His Graduate Work (1969-72)

  • 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


His graduate work 1974 75
His Graduate Work (1974-75)

Most of his work with Prof. Stork concentrated of the formation of Gibberellic Acids B-C-D ring:

  • Reductive cyclization of Ethynylketones

  • 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


Independent Researcher

Vanderbilt University

Columbia University


His work at vanderbilt university 1975 76
His Work at Vanderbilt University (1975-76)

  • Organocuprates 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


His work at vanderbilt university 1975 761
His Work at Vanderbilt University (1975-76)

  • AllyloxyCarbanions:

    • Cyclization to vinyl oxetans via allyloxycarbanions :

    • Selective fomation of the more strained oxetane as long

    • as the addition produces the cis ring juncture

Still C.W., Tetrahedron Letters, 1976, 25, 2115 & Still, W.C.; Macdonald, T.L.; J. Org. Chem., 1976, 41(22), 3620.


His work at vanderbilt university 1975 762
His Work at Vanderbilt University (1975-76)

  • Claisen Variant:

  • Tin chemistry (stannylation/destannylation)

    • α-AlkoxyOrganolithium Reagents

Still, C.W.; Schneider, M.J., JACS, 1977,99(3), 948 & Still, C.W., JACS, 1978, 100 (5), 1481


His work at vanderbilt university 1975 763
His Work at Vanderbilt University (1975-76)

  • Tri-alkyl tin anions undergo high yield conjugate addition to α,β-enones to give

  • the regiospecificenolate

42

40

41

  • Alkylstannanes are smoothly oxidized by chromic anhydride/pyridine to the

  • corresponding ketone

  • Alkylation and oxidation – efficient dialkylativeenone transposition

Still, C.W., JACS, 1977, 99(14), 4836


Columbia university 1977 1998
Columbia University (1977-1998)

  • Anionic [2,3]-sigmatropic rearrangements

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


Columbia university 1977 19981
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 131 072 stereoisomers can exist

1) Still, C.W.; Kahn, M.; Mitra, A., J. Org. Chem., 1978, 43(14), 2923 2) Still, W. C.; Dongwei, J. Org. Chem., 1988,53, 4643 3) Still, W.C.; MacDonald, J.H.III; Collum, D.B.; JACS, 1980, 102(6), 2117 4) Still, W.C.; MacDonald, J.H.III; Collum, D.B.; JACS, 1980,102(6), 2118 5)Still, W.C.; MacDonald, J.H.III; Collum, D.B.; JACS, 1980, 102(6), 2120


Columbia university 1977 19982
Columbia University (1977-1998)

  • Direct Synthesis of Z-unsaturated esters; a useful modification of the

  • Horner-Emmons Olefination

Horner-Wadsworth-Emmons

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


Z trisubstituted allylic alcohols via the wittig reaction
Z-trisubstitutedAllylic 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


Z trisubstituted allylic alcohols via the wittig reaction1
Z-trisubstitutedAllylic Alcohols via the Wittig Reaction

  • Noβ-oxidoYlide intermediate or n-BuLi required

α

Counterion effect

Phosphoniumfluoroborate

Vs

Phosphonium halide

α ‘

α-santalol

Sreekumar, C.; Darst, K.P.; Still, W.C., J. Org. Chem, 1980, 45(21), 4260


Columbia university 1977 19983
Columbia University (1977-1998)

  • Dichlorocarbenecyclopropanation 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


Columbia university 1977 19984
Columbia University (1977-1998)

  • A highly stereoselective synthesis of trans epoxides via arsoniumYlides

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


Columbia university 1977 19985
Columbia University (1977-1998)

  • Synthesis of MacrocyclicTrichothecanoids: 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


Macrocycles
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



9 membered rings
9-Membered Rings

Still, W.C.; Galynker, I., Tetrahedron, 1981, 37 (23), 3981


Peripheral vs antiperipheral attack
Peripheral vsAntiperipheral 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


Periplanone b total synthesis and structure of the sex excitant pheromone of the american cockroach
Periplanone B- Total synthesis and structure of the Sex Excitant Pheromone of the American Cockroach

  • Female species of Periplanetaamericana, 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


Periplanone b first diastereomer
Periplanone B – First Diastereomer

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


Periplanone b stereocontrol approach
Periplanone B – Stereocontrol Approach

X

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


Periplanone b first diastereomer1
Periplanone B – First Diastereomer

Spectral comparison with

authentic Periplanone-B

concludes they are

Unidentical


Periplanone b first diastereomer2
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


Periplanone b second diastereomer
Periplanone B – Second Diastereomer

  • 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


Periplanone b third diastereomer
Periplanone B -Third Diastereomer

  • Construction of the stereoisomeric C-2 – C-3 cisepoxide:

    • 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


Periplanone b third diastereomer1
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


Columbia university 1977 19986
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


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), 10922 & 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


Complex synthetic chemical libraries indexed with molecular tags
Complex Synthetic Chemical Libraries Indexed with Molecular Tags

  • Spaciallysegrated 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


Complex synthetic chemical libraries indexed with molecular tags1
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 = 1 048 576 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


Result analysis
Result Analysis tags

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


General method for molecular tagging of encoded combinatorial libraries
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


Fluorescent sequence selective peptide detection by synthetic small molecules
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, 279 5352), 851


Chemosensors
Chemosensors Synthetic Small molecules

Chemosensor A

Chemosensor B

Dabcyl N-hydrosuccinamide ester

Q = COC6H4N=NC6H4NMe2

F = (CH2)2NH-SO2C10H6NMe2

Dansylsulfonamide of ethanolamine


Fluorescent sequence selective peptide detection by synthetic small molecules1
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


New fluorencent chemosensors with improved photobleaching resistance
New Synthetic Small moleculesFluorencentChemosensors with Improved Photobleaching Resistance

  • Photobleaching: is the photochemical destruction of a fluorophore.

    • Major problem with chemosensors that report binding via fluorescence trough UV

  • 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


New fluorencent chemosensors with improved photobleaching resistance1
New Synthetic Small moleculesFluorencentChemosensors with Improved Photobleaching Resistance

Dansylfluorofore 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


Dansyl vs acridone moiety
Dansyl Synthetic Small moleculesvsAcridone Moiety

  • Replacement of the dansylfluorophore 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


New fluorencent chemosensors with improved photobleaching resistance2
New Synthetic Small moleculesFluorencentChemosensors with Improved Photobleaching Resistance

Receptor binding saturation experiment.

  • Receptor is now more resistant to fluorophorephotobleaching.

  • 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


Conclusion
Conclusion Synthetic Small molecules

  • 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.....


Prof. Louis Synthetic Small moleculesBarriault

Graduate students

Jason Poulin

Minaruzaman

KassandraLepack

Francis Barabé

ChristianeGrisé-Bard

Eric Beaulieu (Past)

Marie-Christine Brochu (Past)

Steve Arns (Past)

Undergrads

Anne-Catherine Bédard

GrabrielBellavance

Jean-Francois Vincent-Rocan

Olivier Gagné

Patrick Lévesque (Past)


Monensine
Monensine Synthetic Small molecules

  • 17 asymmmetric centers, 26 carbon backbone

  • theoretically 131 072 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


Retrosynthetic pathway
Retrosynthetic Synthetic Small molecules Pathway

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


Monensin chromic acid degradation
Monensin Synthetic Small molecules- 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


Monensin further degradation
Monensin Synthetic Small molecules – Further Degradation

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


Monensin retrosynthetic scheme
Monensin Synthetic Small molecules- Retrosynthetic Scheme

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


Monensin further degradation1
Monensin Synthetic Small molecules- Further Degradation

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


Monensin further degradation2
Monensin Synthetic Small molecules- Further Degradation

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


Monensin retrosynthetic scheme1
Monensin Synthetic Small molecules- Retrosynthetic Scheme

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


Forward synthesis
Forward Synthesis Synthetic Small molecules

Collum, D.B.; McDonald, J.H.III;

Still, W.C., JACS, 1980, 102(6), 2118


Forward synthesis1
Forward Synthesis Synthetic Small molecules

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


Forward synthesis2
Forward Synthesis Synthetic Small molecules

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


Forward synthesis3
Forward Synthesis Synthetic Small molecules

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


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