Enantiospecific total syntheses of meroterpenoids (−)-F1839-I and (−)-corallidictyals B and D

Abstract

Enantiospecific total syntheses of spiromeroterpenoid natural products (-)-F1839-I and (-)-corallidictyals B and D were achieved using the environmentally benign and highly atom economical Lewis acid catalysed Friedel-Crafts reaction and a highly regio- and stereoselective spirocyclic C-O bond formation reaction.

Diastereoselective Synthesis of Spirodihydrobenzofuran Analogues of the Natural Product Filifolinol

“…[32] An interesting Niodosuccinimide-triphenylphosphine (NIS-PPh 3 ) system, as a selective reagent for the spiroannulation reaction was introduced for the total synthesis of Corallidictyal D, [33] a spirosesquiterpene aldehyde isolated from the marine sponge Aka coralliphaga with protein kinase inhibitory activity. [34] Using the same system ( À )-F1839-I and Corallidictyal B and C were also successfully synthesized [35,36] (Figure 3).…”

“…A palladium-catalyzed direct cross-coupling reaction of tosylhydrazone and a substituted iodobenzaldehyde, [38] or Friedel-Craft variation using alcohols as alkylating agents instead of alkyl halides. [35] In 2010, the palladium-catalyzed CÀ H activation/CÀ O cyclization reaction for the construction of dihydrobenzofuran compounds was reported by the group of Yu. [39] CÀ H activation has evolved as an environmentally-benign and step-economical synthetic approach with interesting application to the synthesis of complex natural products.…”

“…Moreover, depending of the substitution pattern several steps are required to form the corresponding alkyl halide, necessary for the Friedel‐Crafts alkylation reaction, although interesting variations have been reported. A palladium‐catalyzed direct cross‐coupling reaction of tosylhydrazone and a substituted iodobenzaldehyde, [38] or Friedel‐Craft variation using alcohols as alkylating agents instead of alkyl halides [35] . In 2010, the palladium‐catalyzed C−H activation/C−O cyclization reaction for the construction of dihydrobenzofuran compounds was reported by the group of Yu [39] .…”

A Synthetic Approach Toward a Brominated Oxocane Labdane Diterpenoid Isolated From Laurencia obtusa

“…The oxocane ring might be constructed by RCM of the diene 6, which in turn might be obtained by installation of two olefinic side chains into the Wieland-Miescher ketone derivative 7. 11 Although the hydroxyketone 12 is a known compound derived from Wieland-Miescher ketone (8) and was employed as a starting material for synthetic studies of several natural products, [12][13][14] we took an alternative Wieland-Miescher ketone derivative 7 as our starting material, which is easy to obtain in high enantiomeric excess (Scheme 2). 11 Regioselective protection of the carbonyl group at C9 of the ketone 7 was carried out simply with ethylene glycol in the presence of a catalytic amount of dcamphorsulfonic acid without employing solvent under reduced pressure at 40°C.…”

Enantioselective Total Synthesis and Assignment of the Absolute Configuration of the Meroterpenoid (+)-Taondiol

“…Based on our analysis, a synthetic strategy for (+)-taondiol (4) was envisaged to happen via C−O cyclizaton of the intermediate 10 to form the pyran ring. Compound 10 could be synthesized by a Friedel−Crafts reaction 9 between terpenoid 11 and quinol derivative 12 (Scheme 2). The terpenoid moiety 11, the most challenging part of the synthesis, could be obtained from enantiopure Wieland−Miescher ketone derivative 14 by Robinson-type annulation followed by a few functional group transformations.…”