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Related Concept Videos

Vicinal Diols via Reductive Coupling of Aldehydes or Ketones: Pinacol Coupling Overview01:27

Vicinal Diols via Reductive Coupling of Aldehydes or Ketones: Pinacol Coupling Overview

Wilhelm Rudolph Fittig discovered the pinacol coupling reaction in 1859. It is a radical dimerization reaction and involves the reductive coupling of aldehydes or ketones in the presence of hydrocarbon solvent to yield vicinal diols.
¹H NMR: Long-Range Coupling01:27

¹H NMR: Long-Range Coupling

The coupling interactions of nuclei across four or more bonds are usually weak, with J values less than 1 Hz. While these are usually not observed in spectra, the presence of multiple bonds along the coupling pathway can result in observable long-range coupling.
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Alkynes to Carboxylic Acids: Oxidative Cleavage02:01

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Alkynes undergo oxidative cleavage in the presence of oxidizing reagents like potassium permanganate and ozone. The triple bond — one σ bond and two π bonds — is completely cleaved, and the alkyne is oxidized to carboxylic acids. When warm and basic aqueous potassium permanganate is used as an oxidizing agent, alkynes are first converted to carboxylate salts via an unstable α-diketone intermediate. Further, a mild acid treatment protonates the carboxylate anions generating free carboxylic acid...
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Introduction
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Introduction
One of the convenient methods for the preparation of aldehydes and ketones is via hydration of alkynes. Hydroboration-oxidation of alkynes is an indirect hydration reaction in which an alkyne is treated with borane followed by oxidation with alkaline peroxide to form an enol that rapidly converts into an aldehyde or a ketone. Terminal alkynes form aldehydes, whereas internal alkynes give ketones as the final product.
Reduction of Alkenes: Asymmetric Catalytic Hydrogenation02:17

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Catalytic hydrogenation of alkenes is a transition-metal catalyzed reduction of the double bond using molecular hydrogen to give alkanes. The mode of hydrogen addition follows syn stereochemistry.
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Retropinacol/Cross-pinacol Coupling Reactions - A Catalytic Access to 1,2-Unsymmetrical Diols
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Revealing coupling patterns in isoprenoid alkylation biocatalysis.

Christopher T Walsh1

  • 1Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, Massachusetts 02115, USA. christopher_walsh@hms.harvard.edu

ACS Chemical Biology
|May 24, 2007
PubMed
Summary

Isoprenoid natural products, like taxol, showcase diverse structures. New research reveals that dimerization of isopentenyl diphosphate (IPP) monomers creates novel C10 monoterpene scaffolds through irregular coupling patterns.

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Area of Science:

  • Biochemistry
  • Natural Product Chemistry
  • Organic Synthesis

Background:

  • Isoprenoids are a vast class of natural products (>50,000) with diverse structures and functions, exemplified by taxol.
  • Most isoprenoids are synthesized via iterative head-to-tail enzymatic coupling of isopentenyl diphosphate (IPP) monomers.

Purpose of the Study:

  • To investigate alternative pathways for isoprenoid scaffold assembly.
  • To identify novel coupling patterns beyond the canonical head-to-tail enzymatic reactions.

Main Methods:

  • Analysis of enzymatic reactions involving isopentenyl diphosphate (IPP) monomers.
  • Characterization of C10 monoterpene scaffold formation through dimerization.

Main Results:

  • Demonstration of three distinct "irregular" coupling patterns in C10 monoterpene scaffold formation.
  • Identification of IPP dimerization as a key mechanism for these novel patterns.
  • Expansion of known isoprenoid assembly mechanisms beyond iterative head-to-tail reactions.

Conclusions:

  • IPP dimerization provides a new route to diverse isoprenoid structures.
  • This discovery expands the known biosynthetic pathways for natural products.
  • Understanding these irregular coupling patterns is crucial for natural product synthesis and discovery.