Bioinspired Synthesis of Spirochensilide A from Lanosterol

Abstract

A bioinspired synthesis of spirochensilide A from commercially available lanosterol is reported. The synthesis features a directed C–H oxidation, a Wagner–Meerwein-type double methyl migration, a Meinwald rearrangement, and a double-bond isomerization/spiroketal formation cascade. The proposed biosynthetic speculation was modified by this synthetic sequence, which also served as a platform for the synthesis of other lanostanes with migrating methyl groups.

Direct synthesis of oxaspirolactones in batch, photoflow, and silica gel-supported solvent-free conditionsviavisible-light photo- and heterogeneous Brønsted acid relay catalysis

“…A macrocyclic oxaspirolactone was also reported in 2018 with the isolation of the spirokermeline cyclophane. 5 In more structurally complex natural products, the title motif is present in dammarane-type triterpenoids, namely in phainanoids A–F, 6 and in the rearranged triterpenoid spirochensilide A, 7 which possess immunosuppressive and mild anti-inflammatory activities, respectively.…”

Biogenesis-Inspired Synthesis of Penicillitone

“…Tracing back these natural products to commercially available steroids make short and efficient routes possible, when methods are at hand to establish the necessary C–C bond scissions and migrations. 4 5 6 7 8…”

Asymmetric Total Synthesis of Neobraclactone C

“…Finally, silyl ether cleavage by n-Bu 4 NF/AcOH conditions produced neobraclactone C (1) and 22-epi-neobraclactone C (1′) successfully. 20 In summary, we have accomplished the first total synthesis of neobraclactone C in 22 linear steps from known diol 10, which features a CeCl 3 -catalyzed cyclization in forming contiguous tricyclic stereocenters and an intermolecular Heck coupling/ketal formation/reduction/oxidation strategy in connecting the left and right wings by constructing the pyrone conjunction. However, this synthesis gave a C12 diastereomeric mixture.…”

“…The temperature optimization was detailed in Table S4 of the Supporting Information using compound 30′ as an example. Finally, silyl ether cleavage by n -Bu 4 NF/AcOH conditions produced neobraclactone C ( 1 ) and 22- epi -neobraclactone C ( 1′ ) successfully …”