Baeyer–Villiger oxidation of 163 afforded a separable mixture of lactone 164.
Alkylation of the lactone with LDA and MeI and equilibration of the resulting
epimeric lactones gave the dimethylacetal, which upon ozonolysis under the
Deslongchamps conditions (O 3 /O 2 ) provided the Prelog–Djerassi lactone methyl
ester 165.
Santelli et al. have also reported another convenient synthesis of the
Prelog–Djerassi lactone from a cyclopentanone derivative via Baeyer–Villiger
oxidation [74] (Scheme 31). Addition of crotyl Grignard reagent to 2-alkylidene5-methylcyclopentanones 166 followed by dehydration afforded triene 167. A
conjugate addition of the 1,3-diene moiety gave a 1:1 diastereomeric mixture of
1,5-dienes, which underwent ozonolysis to provide the corresponding
cyclopentanone derivative 163 as a single diastereomer. Finally, Baeyer–Villiger
oxidation of 163 furnished lactone 164, a well-known precursor of the
Prelog–Djerassi lactone.
Adger et al. have reported an enantioselective method for the synthesis of
δ-lactones via application of enzymatic Baeyer–Villiger oxidation [75]
(Scheme 32). Oxidation of cyclopentanone derivative 168 using a monooxygenase
Scheme 30 Santelli and Hacini synthesis of the Prelog–Djerassi lactone
Scheme 31 Santelli et al. approach to the synthesis of Prelog–Djerassi lactone
Synthesis of Saturated Six-Membered Ring Lactones
115
Alkylation of the lactone with LDA and MeI and equilibration of the resulting
epimeric lactones gave the dimethylacetal, which upon ozonolysis under the
Deslongchamps conditions (O 3 /O 2 ) provided the Prelog–Djerassi lactone methyl
ester 165.
Santelli et al. have also reported another convenient synthesis of the
Prelog–Djerassi lactone from a cyclopentanone derivative via Baeyer–Villiger
oxidation [74] (Scheme 31). Addition of crotyl Grignard reagent to 2-alkylidene5-methylcyclopentanones 166 followed by dehydration afforded triene 167. A
conjugate addition of the 1,3-diene moiety gave a 1:1 diastereomeric mixture of
1,5-dienes, which underwent ozonolysis to provide the corresponding
cyclopentanone derivative 163 as a single diastereomer. Finally, Baeyer–Villiger
oxidation of 163 furnished lactone 164, a well-known precursor of the
Prelog–Djerassi lactone.
Adger et al. have reported an enantioselective method for the synthesis of
δ-lactones via application of enzymatic Baeyer–Villiger oxidation [75]
(Scheme 32). Oxidation of cyclopentanone derivative 168 using a monooxygenase
Scheme 30 Santelli and Hacini synthesis of the Prelog–Djerassi lactone
Scheme 31 Santelli et al. approach to the synthesis of Prelog–Djerassi lactone
Synthesis of Saturated Six-Membered Ring Lactones
115