Total Synthesis of Lobatoside E, A Potent Antitumor Cyclic Triterpene Saponin

Abstract

Lobatoside E, a novel and complex cyclic triterpene saponin showing potent antitumor activities, has been synthesized for the first time, employing a highly modular approach. The synthesis, starting with oleanolic acid, D-glucose, D-galactose, L-arabinose, and L-rhamnose, requires a total of 73 steps, with the longest linear sequence of 31 steps and in 1.2% overall yield.

Asymmetric Total Synthesis of the Indole Diterpene Alkaloid Paspaline

“…In 2008, Yu and co-workers reported a stoichiometric desymmetrization of dimethyl oxime 79 , proceeding in 72% yield and complete selectivity (assisted by the conformational rigidity of 79 ) en route to the synthesis of lobatoside E. 36 Six years later, the Sorenson laboratory described the first symmetry-breaking implementation of Sanford’s catalytic reaction in their synthesis of jiadifenolide. 37 In this reaction, treating oxime 81 with Pd(OAc) 2 and PhI(OAc) 2 afforded the desired acetate 82 in 22% yield and 1:1 dr.…”

Total synthesis and antiviral activity of indolosesquiterpenoids from the xiamycin and oridamycin families

“…O -Methyloxime formation afforded the substrate suitable for a directed C–H bond oxidation, and Sanford’s conditions [Pd(OAc) 2 (20 mol%), PhI(OAc) 2 ]6061 were effective to give the desired acetate 31 with good overall efficiency. It should be noted that stoichiometric Pd-mediated Csp 3 –H bond oxidation reactions have been exploited in terpenoid synthesis416263. Deprotection of the oxime and acetate, followed by reduction and desulfonylation, afforded diol 32 with acceptable overall efficiency.…”

Chemical Synthesis of Saponins

“…32 Peracetylation followed by bromination at the anomeric position and subsequent orthoester formation yielded the fully protected L-arabinose derivative 27. Substitution of the 3,4-O-Ac group by 3,4-O-Bn furnished compound 28 in high yield.…”

“…149 In 2008, Zhu, Tang, and Yu accomplished its total synthesis, based on a linear assembly strategy that started from bayogenin derivative 21 (Scheme 43). 32 Condensation of this aglycone (21) with the L-arabinopyranosyl bromide 29 under phasetransfer conditions provided the desired monodesmoside 28-arabinosyl ester, which was subsequently glycosylated at the 3-OH position with the glucosyl imidate 286, under TMSOTf promotion. The corresponding 3,28-O-bidesmoside 287 was obtained in excellent yield.…”