From D-camphor to the taxanes. Highly concise rearrangement-based approaches to taxusin and taxol

Paquette, L. A.; Zhao, Mangzhu; Montgomery, Francis; Zeng, Qingbei; Wang, T. Z.; Elmore, Steven W.; Combrink, Keith D.; Wang, H.-L.; Bailey, Simon; Su, Zhuang

doi:10.1351/pac199870081449

Cited by 14 publications

(7 citation statements)

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“…Synthetic Considerations. Enantiopure bicyclic ketone 14 , which is readily available from d -camphor-10-sulfonyl chloride, offers several advantages as a starting material for this investigation: (1) it is amenable to conversion to keto aldehyde 15 by direct ozonolysis; (2) the latter can be chemoselectively olefinated with the p -methoxy-phenoxy (OPMP) ylide 16 and its sulfur equivalent 17 with generation of chromatographically separable E / Z isomer pairs; (3) the presence of apical methyl groups in 14 and its homologues serves to relegate entry of ( Z )-1-propenylmagnesium bromide (necessarily in the presence of anhydrous cerium trichloride in order to deter enolization) exclusively to the endo surface; and (4) the structural features of 9 − 13 were expected to lend themselves to [3,3] sigmatropic rearrangement exclusively via an endo-chair transition state 21 because no exception to the adoption of this reaction trajectory by related compounds is currently known …”

Section: Resultsmentioning

confidence: 99%

High-Rate Accelerations in Oxy-Cope Rearrangements Induced by Sulfur Substitution: Kinetic Study Involving Electronically and Geometrically Differentiated 1-Alkenyl-2-(Z-1-propenyl)-7,7-dimethyl-exo-norbornan-2-ols

et al. 2000

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The rates of anionically promoted oxy-Cope rearrangement of five structurally related exonorbornanols have been determined. A critical difference in the substitution pattern of these substrates is the presence or absence of oxygen or sulfur functionality at the terminal carbon of the bridgehead vinyl group and the geometric nature of the olefinic center. The results convincingly establish that although an OPMP substituent exerts, at best, a very modest decelerative kinetic effect, the presence of the PhS substituent causes rearrangement to occur approximately 10 3 times faster by lowering the activation energy to the extent of 3-4 kcal/mol. This remarkable divergence in behavior is shown to correlate well with the highly dissociative nature of the transition state that is predicted computationally.

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Section: Resultsmentioning

confidence: 99%

High-Rate Accelerations in Oxy-Cope Rearrangements Induced by Sulfur Substitution: Kinetic Study Involving Electronically and Geometrically Differentiated 1-Alkenyl-2-(Z-1-propenyl)-7,7-dimethyl-exo-norbornan-2-ols

et al. 2000

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“…Camphor is known as the naturally available starting material in a number of syntheses of more complex compounds from the middle of the XIX century. Nowadays many syntheses of steroids [1][2][3], terpenoids [4][5][6][7][8][9][10][11][12], vitamins [13][14][15] and other natural products [16][17][18][19] that involve camphor or its derivatives are described in the literature.…”

Section: Introductionmentioning

confidence: 99%

Recyclization reactions of 8,10-dibromocamphor with Grignard and organolithium compounds

Verenka

Gorichko

2021

Fr. Ukr. J. Chem.

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Grignard reagents and organolithium compounds react with 8,10-dibromocamphor to afford substituted 1-methyl-2-methylenebicyclo[3.2.0]heptanes. Recyclization proceeds via intramolecular enolate alkylation and Grob fragmentation of the reaction intermediates. All compounds have been characterized by 1H, 13C and 19F NMR spectroscopy and their chemical composition proved by HRMS analyses. The relative spatial arrangement of substituents in the molecule of (1-methyl-2-methylenebicyclo[3.2.0]heptan-6-yl)diphenylmethanol was studied by NOESY experiments.

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“…The Wagner–Meerwein and Nametkin-type rearrangements are the most common reaction patterns [ 6 ] and the addition of organometallic reagents to the camphor carbonyl group allows for selective introduction of additional substituents and functional groups (e.g., as in [ 7 ]). Camphor was the source of chirality in Holton’s taxol synthesis [ 8 ] and other approaches to the taxane group of compounds [ 9 – 11 ].…”

Section: Introductionmentioning

confidence: 99%

Synthesis of alkynyl-substituted camphor derivatives and their use in the preparation of paclitaxel-related compounds

Carvalho

Herrmann

Wagner

2017

Beilstein J. Org. Chem.

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Compounds containing two alkyne groups in close vicinity at the rigid skeleton of camphorsulfonamide show unique reactivities when treated with electrophiles or catalytic amounts of platinum(II). The formed product structures depend not only on the reagents used but also on the substituents attached to the triple bonds. Cycloisomerisations with perfect atom economy lead to polycyclic heterocycles that resemble to some extent the AB ring system of paclitaxel. Herein, we present practical synthetic methods for the selective synthesis of precursor dialkynes bearing different substituents (alkyl, aryl) at the triple bonds, based on ketals or an imine as protecting groups. We show for isomeric dialkynes that the reaction cascade induced by Pt(II) includes ring annulation, sulphur reduction, and ring enlargement. One isomeric dialkyne additionally allows for the isolation of a pentacyclic compound lacking the ring enlargement step, which we have proposed as a potential intermediate in the catalytic cycle.

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From D-camphor to the taxanes. Highly concise rearrangement-based approaches to taxusin and taxol

Abstract: Abstract

Cited by 14 publications

References 0 publications

High-Rate Accelerations in Oxy-Cope Rearrangements Induced by Sulfur Substitution: Kinetic Study Involving Electronically and Geometrically Differentiated 1-Alkenyl-2-(Z-1-propenyl)-7,7-dimethyl-exo-norbornan-2-ols

High-Rate Accelerations in Oxy-Cope Rearrangements Induced by Sulfur Substitution: Kinetic Study Involving Electronically and Geometrically Differentiated 1-Alkenyl-2-(Z-1-propenyl)-7,7-dimethyl-exo-norbornan-2-ols

Recyclization reactions of 8,10-dibromocamphor with Grignard and organolithium compounds

Synthesis of alkynyl-substituted camphor derivatives and their use in the preparation of paclitaxel-related compounds

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