Recent advances in the Overman rearrangement: synthesis of natural products and valuable compounds

Fernandes, Rodney A.; Kattanguru, Pullaiah; Gholap, Sachin P.; Chaudhari, Dipali A.

doi:10.1039/c6ob02625g

Cited by 47 publications

(18 citation statements)

References 340 publications

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“…Sabinol was transformed into trichloroacetimidate 2 in the presence of trichloroacetonitrile and DBU as a strong base ( Scheme 1 ) [ 8 , 11 ]. 2 underwent Overman rearrangement by heating in the presence of K 2 CO 3 , resulting in protected allylamine 3 [ 42 ]. Since we have found difficulties during the deprotection of N -trichloroacetyl aminodiols in our recent studies [ 8 ], we have changed the protecting group to Boc in a two-step process via enamine 4 .…”

Section: Resultsmentioning

confidence: 99%

Stereoselective Syntheses and Application of Chiral Bi- and Tridentate Ligands Derived from (+)-Sabinol

et al. 2018

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A library of bidentate diols, as well as tridentate triols and aminodiols, derived from (+)-sabinol, was synthesized in a stereoselective manner. Sabinol was transformed into allylic trichloroacetamide via Overman rearrangement of the corresponding trichloroacetimidate. After changing the protecting group to Boc, the enamine was subjected to stereospecific dihydroxylation with OsO4/NMO, resulting in the (1R,2R,3R,5R)-aminodiol diastereomer. The obtained primary aminodiol was transformed to a secondary analogue. The ring closure of the N-benzyl-substituted aminodiol with formaldehyde was investigated and regioselective formation of the spiro-oxazolidine ring was observed. Hydroboration or dihydroxylation of sabinol or its benzyl ether with OsO4/NMO resulted in the formation of sabinane-based diols and triols following a highly stereospecific reaction. Treatment of sabinol with m-CPBA afforded O-benzoyl triol as a diastereoisomer of the directly dihydroxylated product, instead of the expected epoxy alcohol. The resulting aminodiols, diol, and triols were applied as chiral catalysts in the reaction of diethylzinc and benzaldehyde from moderate to good selectivity.

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Section: Resultsmentioning

confidence: 99%

Stereoselective Syntheses and Application of Chiral Bi- and Tridentate Ligands Derived from (+)-Sabinol

et al. 2018

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“…In the event, [3,3]-sigmatropic allylic imidate rearrangement 32 of trichloroacetimidate 10 proceeded efficiently, appropriately shifting the chirality from the R-secondary alcohol to the key S-trichloroacetamide 11 in 92% yield, with the absolute stereochemistry being cemented by X-ray crystal structure determination of 11b (Scheme 6 and SI). The thermal [3,3]-sigmatropic rearrangement of allylic trichloroacetimidates 33 is known to proceed stereospecifically in a synfacial fashion on 6membered ring systems such as cyclohexenes 30,34 and dihydropyrans. 35 DFT calculations suggest that such rearrangements typically proceed asynchronously, via a pseudo-pericyclic transition state (Scheme 6).…”

Section: Resultsmentioning

confidence: 99%

Rapid Enantioselective and Diastereoconvergent Hybrid Organic/Biocatalytic Entry into the Oseltamivir Core

et al. 2021

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A formal synthesis of the anti-viral drug (-)-oseltamivir (Tamiflu ® ) has been accomplished starting from m-anisic acid via dissolving metal or electrochemical Birch reduction. The correct absolute stereochemistry is efficiently set through enzyme-catalyzed carbonyl reduction on the resultant racemic a,bunsaturated ketone. A screen of a broad ketoreductase (KRED) library identified several that deliver the desired allylic alcohol with nearly perfect facial selectivity at the new center for each antipodal substrate, indicating that the enzyme also is able to completely override inherent diastereomeric bias in the substrate. Conversion is complete with D-glucose serving as terminal hydride donor (glucose dehydrogenase). For each resulting diastereomeric secondary alcohol, O/N-interconversion is then efficiently effected either by synfacial [3,3]-sigmatropic allylic imidate rearrangement or by direct, stereo-inverting N-Mitsunobu chemistry. Both stereochemical outcomes have been confirmed crystallographically. The a,b-unsaturation is then introduced via an a-phenylselenylation/oxidation/pyrolysis sequence to yield the targeted (S)-N-acyl-protected 5-amino-1,3-cyclohexadiene carboxylates, key advanced intermediates for oseltamivir pioneered by Corey (N-Boc) and Trost (N-phthalamido), respectively. ASSOCIATED CONTENT Supporting informationSupporting Information is available free of charge on the ACS Publications website: Procedural details, KRED screening, NMR spectra, HPLC traces, X-ray crystal structure details (50 pages).

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“…However, this approach met with limited success and required peculiar N -nucleophiles and use of catalysts, affording mostly moderate yields of α/β anomeric mixtures . The O -allyl to N -allyl rearrangements (cyanate/isocyanate or Overman), reliable methods for introducing nitrogen moieties on allyl alcohol skeletons with high degree of stereochemical control, might serve the purpose. These methods are largely neglected in synthesis; particularly, the allyl cyanate/isocyanate rearrangement has been used in limited examples of elegant syntheses mainly by Ichikawa following his reliable procedure for generating the required cyanate functionality , and more recently by Stecko’s and Carreaux’s groups .…”

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Allyl Cyanate/Isocyanate Rearrangement in Glycals: Stereoselective Synthesis of 1-Amino and Diamino Sugar Derivatives

et al. 2020

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The [3,3]-sigmatropic allyl cyanate/isocyanate rearrangement of glycals in the presence of O -, N -, and C -nucleophiles afforded β- N -glucosyl and galactosyl carbamates, ureas, and amides in good yields. The unsaturated products were elaborated to N -glycosides by dihydroxylation, to 1,3-diaminosugars by tethered aminohydroxylation, or to 1,2-diaminosugars by iteration of the sigmatropic rearrangement. This metal-free methodology represents an excellent and general method for the stereoselective synthesis of N -glycosides and diamino sugars with complete transmission of stereochemical information.

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Recent advances in the Overman rearrangement: synthesis of natural products and valuable compounds

Cited by 47 publications

References 340 publications

Stereoselective Syntheses and Application of Chiral Bi- and Tridentate Ligands Derived from (+)-Sabinol

Stereoselective Syntheses and Application of Chiral Bi- and Tridentate Ligands Derived from (+)-Sabinol

Rapid Enantioselective and Diastereoconvergent Hybrid Organic/Biocatalytic Entry into the Oseltamivir Core

Allyl Cyanate/Isocyanate Rearrangement in Glycals: Stereoselective Synthesis of 1-Amino and Diamino Sugar Derivatives

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