Asymmetric synthesis of trans-4,5-disubstituted γ-butyrolactones involving a key allylboration step. First access to (−)-nicotlactone B and (−)-galbacin

Abstract

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Stereoselective Synthesis of Tetrahydrofuran Lignans

“…In 2018, an asymmetric synthesis of (-)-galbacin through an efficient synthesis of chiral 4,5-anti-disubstituted γ-butyrolactone 55 obtained from enantioenriched γcarbamate alkenylboronates 53 was reported by Carreaux and co-workers (Scheme 12). 19 The cornerstone of their strategy was the implementation of sequential one-pot transformations of 53 into 54 via a [3,3]-allyl cyanate rearrangement/allylboration/nucleophilic addition/cyclization. Dehydration of carbamate (S,E)-53 (98% ee) mediated by TFAA produced cyanate S which further underwent [3,3]allyl cyanate rearrangement to give α-isocyanato allylboronate T. Without purification, allylboration of T with 3,4-(methylenedioxy)benzaldehyde provided adduct U which upon addition of methanol (1 equiv) gave the acyclic enecarbamate V. Treatment of V with HCl gave the cyclized product W, which was efficiently transformed into the corresponding methyl acetal 54 using excess methanol and HCl.…”

Synthesis of novel 1,2,3-triazole-based hybrids via click reactions

“…For this reason, research into the development of methods for the synthesis of novel substituted triazoles is constantly increasing. 8,9 Of particular value are studies on the isolation and investigation of substances from natural raw materials that possess cytotoxic, 10 antitumor 11 activities, or being inhibitors of topoisomerase, 12 DPP-4 and cancer cell growth. 13 The main method to prepare 1,2,3-triazoles involves the 1,3-cycloaddition of organic azides with a terminal triple bond, via a click reaction.…”

Stereoselective Sequential Spirocyclopropanation/Cloke–Wilson Rearrangement Reactions for Synthesis of trans-β,γ-Disubstituted γ-Butyrolactones Using Alkylidene Meldrum’s Acid and Benzyl Halides

“…Moreover, it is also an important and versatile building block in organic synthesis . For example, β,γ-disubstituted γ-butyrolactone was one of the key intermediates to prepare lignans of the 2,5-diaryl-3,4-disubstituted tetrahydrofuran framework . Thus, development of efficient approaches to the high-value scaffold has drawn considerable attention, and a plethora of synthetic methods have been reported …”