Syntheses of Gymnothespirolignans B and C and Non-natural Isomer 9-Epi-gymnothespirolignan B

Abstract

Syntheses of polycyclic spiro lignans gymnothespirolignans B and C as well as the unnatural isomer 9-epigymnothespirolignan B were accomplished using (R)-Roche ester and an appropriately substituted fluorenone. Key features of the convergent syntheses include coupling of the fluorenone and an iodo-alkene intermediate derived from (R)-Roche ester in the presence of the Lewis acid TiCl(OiPr) 3 , C9-O bond formation via an S N 2 reaction with retention of stereochemistry, and diastereoselective hydrogenations of a common alkene intermediate guided by accessibility or positioning by the C8-methoxy.

A Domino Radical Amidation/Semipinacol Approach to All‐Carbon Quaternary Centers Bearing an Aminomethyl Group

“…Additional references cited within the Supporting Information. [ 48 , 49 , 50 , 51 , 52 , 53 , 54 , 55 , 56 , 57 , 58 , 59 , 60 , 61 , 62 , 63 , 64 , 65 , 66 , 67 , 68 , 69 , 70 , 71 , 72 , 73 , 74 ]…”

Late-Stage Functionalization: Total Synthesis of Beauveamide A and Its Congeners and Their Anticancer Activities

“…We then concentrated on the synthesis of the β-hydroxy γ-methyl aliphatic acid part following a route other than the existing approach . The known alcohol 17 was oxidized under Swern conditions and subjected further to Bestmann–Ohira reaction to yield alkyne 18 . This was reacted with n- BuLi/EtI to obtain the corresponding ethylated product and subsequently exposed to zipper reaction conditions to transform it into the corresponding terminal alkyne, which was finally reacted with Cp 2 ZrCl/DIBAL-H/I 2 following the Negishi protocol to access vinyl iodide 19 in 59% overall yield.…”