Intramolecular Diels-Alder reaction, Fukuyama

Although the asymmetric total syntheses developed by Nicolaou and by Shair provide easy routes to enantiomerically pure CP compounds, the target molecules (+)-CP-263,114 (ent-1) and (—)-CP-225,917 (ent-2) are only the enantiomers of the natural occurring phomoidrides. After the establishment of the absolute configuration of the CP molecules by chemical synthesis, the focus of synthetic interest is the asymmetric total syntheses of (—)-CP-263,114 (1) and (-l-)-CP-225,917 (2). The first total synthesis furnishing (—)-CP-263,114 (1) as the correct enantiomer has recently been reported by Fukuyama et al. [23]. As the stereoselectivitydetermining step, an intramolecular Diels-Alder reaction was chosen, similar to that in Nicolaou s synthesis (Figure 11). The Diels-Alder precursor 42 is prepared in four easy... 

In 2012, Fukuyama s group reported a novel synthesis route to the spiro-p-lactonic sesquiterpene (-)-anisatin, and they also relied on the construction of a bicyclo[2.2.2]octane system via a DIB-mediated methoxylative phenol dearomatization followed by an intramolecular Diels-Alder reaction [127]. The homochiral phenolic dihydrobenzofuran propargyl ether 231 thus afforded, via the ort/io-quinone monoketal 232 and treatment of its intramolecular [4+2] epimeric cycloadducts with camphorsulfonic acid in MeOH, the bicyclo[2.2.2] octanedienone 234 as a single diastereomer (Fig. 56). Further transformation of 234 gave the vinyl 235, whose trisubstituted double btmd bridge was oxidatively cleaved by mild ozonolysis to furnish the ketoaldehyde 236, en route to (-)-anisatin [127]. 

Intermolecular and Intramolecular Diels-Alder Reactions (-)-Oseltamivir (Fukuyama), Platensimycin (Yamamoto) and 11,12-Diacetoxydrimane (Jacobsen)... 

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