title: Syntheses in enantiopure form of four diastereoisomeric naphthopyranquinones derived from aphid insect pigments.
abstract: The first syntheses are described of the four enantiopure naphthopyranquinones (1R,3R,4S)- and (1R,3R,4R)-3,4-dihydro-4,7,9-trihydroxy-1,3-dimethylnaphtho[2,3-c]pyranquinone (quinone A 1 and quinone A' 2) and their two C-3 epimers, the (1R,3S,4S)- and (1R,3S,4R)-diastereoisomers 5 and 6, using enantiopure lactate as the source of asymmetry. Key factors in these syntheses are the maintenance of stereochemical integrity throughout the sequences and intramolecular diastereoselective cyclisations of the titanium phenolates of phenolic lactaldehydes. For these cyclisations the differing degree of diastereoselectivity is explained as are the stereochemistries of the product 2-benzopyran-4,5-diols.
authors.affiliation: Department of Chemistry, Murdoch University, Murdoch, WA 6150, Australia.
authors.forename: Rachna
authors.initials: R
authors.lastname: Aggarwal
authors.forename: Robin G F
authors.initials: RG
authors.lastname: Giles
authors.forename: Ivan R
authors.initials: IR
authors.lastname: Green
authors.forename: Francois J
authors.initials: FJ
authors.lastname: Oosthuizen
authors.forename: C Peter
authors.initials: CP
authors.lastname: Taylor
mesh_terms: D000818:Animals; D001042:Aphids / Q000737:chemistry*; D003500:Cyclization; D008968:Molecular Conformation; D009285:Naphthoquinones / Q000138:chemical synthesis* / Q000737:chemistry; D010860:Pigments, Biological / Q000737:chemistry*; D011714:Pyrans / Q000138:chemical synthesis* / Q000737:chemistry*; D013237:Stereoisomerism
chemical_list: D009285:Naphthoquinones; D010860:Pigments, Biological; D011714:Pyrans