A new reaction for the preparation of acetylenic alcohols from lactones

Yadav, J. S.; Prahlad, V.; Chander, Madhavi C.

doi:10.1039/c39930000137

Cited by 12 publications

(3 citation statements)

References 10 publications

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“…As expected for an asymmetric hydrogenation, the reaction scaled well. This saturated lactone was then subjected to dichloro‐olefination on reaction with CCl 4 /PPh 3 in THF, and the resulting product 33 was treated, without delay, with lithium sand to furnish alkyne 34 [67,68] . The derived TBDPS‐ether 35 underwent a fully regioselective iodoboration/protodeborylation sequence on successive treatment with 9‐I‐9‐BBN and HOAc [69] .…”

Section: Resultsmentioning

confidence: 99%

“…This saturated lactone was then subjected to dichloro-olefination on reaction with CCl 4 /PPh 3 in THF, and the resulting product 33 was treated, without delay, with lithium sand to furnish alkyne 34. [67,68] The derived TBDPS-ether 35 underwent a fully regioselective iodoboration/protodeborylation sequence on successive treatment with 9-I-9-BBN and HOAc. [69] Metal/halogen exchange of 36 thus formed with tBuLi, transmetalation of the resulting organolithium species with ZnBr 2 and subsequent Negishi coupling [70] with allyl chloride 6 [2] derived from methyl acrylate by a Baylis-Hillman reaction [2,71] opened a convenient gateway to acetate 2.…”

Section: Resultsmentioning

confidence: 99%

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An Efficient and Scalable “Second Generation” Total Synthesis of the Marine Polyketide Limaol Endowed with Antiparasitic Activity

Hess,

Fürstner

2024

Chemistry A European J

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The cluster of four skipped exo‐methylene substituents on the “northern” wing of limaol renders this marine natural product unique in structural terms. This arguably non‐thermodynamic array gains kinetic stability by populating conformations which impede isomerization to a partly or fully conjugated polyene. This analysis suggested that the difficulties encountered in our first total synthesis had not been caused by an overly fragile character of this unusual substructure; rather, an unfavorable steric microenvironment about the spirotricyclic core was accountable. To remedy the issue, the bulky silyl ethers were replaced by acetates; this simple change allowed all problems to be addressed, the overall yield to be multiplied, and the material throughput to be increased more than eighty‐fold per run. Key‐to‐success was a gold‐catalyzed spirocyclization reaction; the reasons why a Brønsted acid cocatalyst is needed and the origin of the excellent levels of selectivity were delineated. The modified protecting group pattern also allowed for a much‐improved fragment coupling process by a reagent controlled asymmetric allylation. Finally, a new route to the “northern” sector was established by leveraging the power of asymmetric hydrogenation of a 2‐pyrone derivative. Limaol was found to combine appreciable antiparasitic activity with very modest cytotoxicity.

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

An Efficient and Scalable “Second Generation” Total Synthesis of the Marine Polyketide Limaol Endowed with Antiparasitic Activity

Hess,

Fürstner

2024

Chemistry A European J

View full text Add to dashboard Cite

show abstract

“…Toma and Li vre and their co-workers found conditions for the transformation of unprotected or partially protected aldopyranoses and -furanoses into terminal acetylenosaccharides; excess BuLi in THF at -70h was used for the elimination step [66,67]. A Corey-Fuchs-type reaction was also described for lactones; lactones were transformed into dichloromethylene derivatives and further by treatment of the halide with Li sand in THF into hydroxyacetylenes (82-88 %) [68].…”

Section: By Eliminationmentioning

confidence: 99%