Efficient synthesis of (±)-γ-lycorane employing stereoselective conjugate addition to nitroolefin

Conjugate Additions of Nitroalkanes to Electron-Poor Alkenes: Recent Results

“…Better diastereoselections can be obtained starting from nitro alcohol 86 that in the same conditions (CsF, R 4 NBr) produces a diastereomeric couple in which compound 87 strongly predominates (Scheme ) 28 …”

“…Better diastereoselections can be obtained starting from nitro alcohol 86 that in the same conditions (CsF, R 4 NBr) produces a diastereomeric couple in which compound 87 strongly predominates (Scheme 28). 89 Allylic alkylation of nitro compounds catalyzed by Pd(0) can be associated with conjugate additions in order to prepare cyclohexane derivatives. Allyl acetate 89 reacts with metal nitronates 90 in the presence of Pd(PPh 3 ) 4 to give an open-chain homoallylic nitro derivative that as soon as it is formed cyclizes by means of a conjugate addition, leading to the diastereomeric couple of nitrocyclohexanes 91 and 92 (Scheme 29).…”

Nitroalkenes as Amination Tools

“…Reduction of the nitro group, followed by lactamization and hydride reduction, generates perhydroindole 122 , and methoxycarbonylation of the pyrrolidine nitrogen provides the requisite substituent for a Pictet -type ring -closure to provide the lactam system, which is then reduced to β -lycorane. The stereoisomeric α -lycorane can be obtained from the minor isomer of the cyclohexanyl nitroester 121 , while utilization of t -butyl 2 -(2 -nitro -2 -cyclohexenyl) acetate in the reaction with the same organolithium derivative provides a route to γ -lycorane [141] .…”

Catalytic asymmetric transformations with fine-tunable biphenol-based monodentate ligands

“…44 Due to its unique pentacyclic structure, (+)-c-lycorane has inspired many synthetic chemists to develop a number of innovative approaches toward its total synthesis. [44][45][46][47][48][49] However, very few approaches to the asymmetric synthesis of this compound have been reported so far. 45,49 In 1995, Mori et al reported the first asymmetric synthesis of (+)-clycorane, featuring a Pd-catalyzed allylic alkylation in the key step, wherein a sequential allylic alkylation, allylic amination, and Heck reaction led to the target pentacyclic system (Scheme 2).…”