Total Synthesis of (±) Maoecrystal V

Abstract

A concise first total synthesis of (±) maoecrystal V (1) is reported. The synthesis features a Wessely oxidative dearomatization of a phenol, an intramolecular Diels-Alder reaction, and a Rh-catalyzed O-H bond insertion as key steps.

Modern Organic Synthesis with α-Diazocarbonyl Compounds

“…The power of the intramolecular process in highly complex cases is beautifully demonstrated by the recent total synthesis by Li and Yang and their co-workers of maoecrystal V (190), a diterpenoid natural product of Chinese herb origin. 512 This molecule possesses a highly congested pentacyclic carbon framework with six stereocenters, three of which are contiguous quaternary carbon atoms. The focus of the key step in the synthesis was a hydroxyl group deeply embedded in the center of this array containing a distal diazoester moiety.…”

Enantioselective Total Synthesis of (+)‐Steenkrotin A and Determination of Its Absolute Configuration

“…The preferred boat transition state 13 B (inw hich the OTBS group occupies an equatorial position), led to the reactionp roceeding exclusively through addition to the less hindered, convex face to give the desired product as as ingle diastereomer. Although tertiarya lcohol 8 appeared to be unstable, its OÀH bond insertion [17] with diazomalonic ester 9 catalyzed by Rh 2 (OAc) 4 took place smoothly to deliver the expected diester 15 in 75 %y ield. After being transformed into diol 16 through methylation and reduction (70 %y ield over the two steps), the two hydroxyl groups were successfully differentiated by as ubstrate-controlled acylation,l eading to monoacetate 17 in 90 % yield (6.2:1 d.r.a tC 6).T he minor isomer C6-epi-17 could be recycled with K 2 CO 3 /MeOH, giving 16 in quantitative yield.…”

Synthetic Strategies toward Natural Products Containing Contiguous Stereogenic Quaternary Carbon Atoms

“…In 2010, Yang and co-workers reported the first total synthesis of racemic maoecrystal V. [94] It was envisioned that the complete ring system would be constructed by intramolecular Diels–Alder reaction of tetraene 136 , which in turn would arise from the coupling of β-ketoester 137 and aryllead intermediate 138 (Scheme 14). [95] …”