A recent example of this approach has been reported by Yang and coworkers
[172] in their synthesis of crassalactone D 338, using m-CPBA as the oxidant
(Scheme 83). Mohapatra et al. [173] used the same conditions in their synthesis
of pyrenolide D (341a), while Robertson et al. [141] have used a furan oxidative
spirocyclization in studies toward the sawaranospirolides (Scheme 84).
An alternative approach to 5,5-spirolactones has been developed by Vassilikogiannakis et al., where HDA of a furan with singlet oxygen followed by intramolecular ring opening and dehydration gives the dihydrofuran spiroacetals 347
or 349 (Scheme 85). This method has been used for the synthesis of crassalactone D
338, as well as two epimeric spiroacetals in a sequence toward pyrenolide D, 354a
and 354b [174].
Scheme 81 Pettus et al.’s [3+2]-cycloaddition-based synthesis of γ-rubromycin [170]
Scheme 82 Furan oxidation approaches for the synthesis of spiroacetals
246
M.A. Brimble and L.A. Stubbing
[172] in their synthesis of crassalactone D 338, using m-CPBA as the oxidant
(Scheme 83). Mohapatra et al. [173] used the same conditions in their synthesis
of pyrenolide D (341a), while Robertson et al. [141] have used a furan oxidative
spirocyclization in studies toward the sawaranospirolides (Scheme 84).
An alternative approach to 5,5-spirolactones has been developed by Vassilikogiannakis et al., where HDA of a furan with singlet oxygen followed by intramolecular ring opening and dehydration gives the dihydrofuran spiroacetals 347
or 349 (Scheme 85). This method has been used for the synthesis of crassalactone D
338, as well as two epimeric spiroacetals in a sequence toward pyrenolide D, 354a
and 354b [174].
Scheme 81 Pettus et al.’s [3+2]-cycloaddition-based synthesis of γ-rubromycin [170]
Scheme 82 Furan oxidation approaches for the synthesis of spiroacetals
246
M.A. Brimble and L.A. Stubbing