Asymmetric diastereoselective syntheses of the aphid insect pigment derivatives quinone A and quinone A′

Syntheses in enantiopure form of four diastereoisomeric naphthopyranquinones derived from aphid insect pigments

“…These compounds 1-4 comprise all four stereoisomers based on 3R stereochemistry. After the completion of this work, 6 discussions with Professor Cameron revealed 7 preliminary observations suggesting that the compounds 3 and 4 are the enantiomers of two further, unreported, derivatives of naturally occurring aphid pigments. The remainder of this paragraph summarizes the hitherto unpublished results of Banks and Cameron.…”

“…While we have previously synthesised 4 the racemates of the quinones 1 and 2, this method did not lend itself to the assembly of the individual enantiomers. 5 In a preliminary publication we have recently reported 6 the first syntheses of each of these enantiopure quinones, as well as those of their C-1 epimers 3 and 4. These compounds 1-4 comprise all four stereoisomers based on 3R stereochemistry.…”

A model for the synthesis of naturally occurring benzisochromenequinones

“…2 The pyran ring of the targets has the potential for three asymmetric centres, and considerable effort has been expended in achieving the desired stereochemistry, both for the racemates [3][4][5][6] and for the enantiopure compounds. [7][8][9] Naturally occurring benzisochromenequinones have also been reported, 1 although their syntheses have hitherto received less attention. Nevertheless, two elegant short assemblies of these compounds from 2-(1'-hydroxyethyl)-1,4-naphthoquinone have been reported recently, 10,11 and the former method extended to the assembly of the related benzisochromanequinones through stereoselective reduction.…”