No abstract

Reduction of 1.4-naphthoquinone epoxide with sodium borohydride (1 equiv.) is shown to give the isomeric r-2.3-epoxy-3.4-dihydro-c-4-hydroxynaphthalen-I (2H)-one ( I I I a ) and r-2,3-epoxy-3,4-dihydro-t-4-hydroxynaphthalen-I (2H)-one ( I I I b ) in a ratio of ca. 11 : 1. With the same reagent juglone epoxide (5-hydroxy-I ,4naphthoquinone epoxide) is selectively and stereospecificalty reduced a t the chelated carbonyl to give r-2.3-epoxy-3,4-dihydro-c-4,5-dihydroxynaphthaten-l(2H) -one (IX) as the major product. The role of the chelating hydroxygroup is discussed. The configurations of the products are established on the basis of the n.m.r. spectra of the corresponding 2.3-epoxy-1.2.3.4-tetrahydronaphthalene-I ,4-diols. N.m.r. evidence also establishes the preferred conformations. THE structures of mycochrysone (I) 3 and cervicarcin (11) contain a 2,3-epoxy-4-hydroxynaphthalen-l(2H)one system [ e g . (111)], the two diastereoisomeric forms of which cannot be easily distinguished by chemical and physical methods4s5 We report the syntheses of compounds (IIIa and b) and describe the properties and stereochemistry of these and related compounds which are of particdar relevance to the stereochemistry of ring D in myochrysone. In this paper we shall refer to compounds such as (IIIa), in which the hydroxy-and Part IT, A. Rashid and G. Read, J . Chem. SOG.

No abstract

Oxidation of linoleic acid using immobilised soybean lipoxygenase-I gave (1 3s) -1 3-hydroxyoctadeca-9,11 -dienoic acid 1 : lactonisation and Diels-Alder reactions involving this hydroxy acid have been explored.

Physical and chemical methods have been used to show that laccaic acid Al, the major pigment of stick lac, is 3-[3-(2-acetamidoethyl) -6-hydroxyphenyl] -l,2,4,7-tetrahydroxyanthraquinone-5,6-dicarboxylic acid. Exeter

H-7).1955.

In experime~lts with C1.l-labelled compounds, shilcimic acid, phenylalanine, phenyllactic acid, and metatyrosine were found to be precursors of the terphenylquinone pigment volucrisporin. It is suggested that the pigment is bias)-nthesized by the self-condensation of t\vo molecules of an unbranched plienylpropanoid intermediate, and that hydrosylation of t h e phenyl rings in the meta position occurs before the condensation step.Several speculative scheines have been proposed for the biogenesis of terpheng-lcluinone pigments. I~ceraldehyde might be involved in the formatiol~ of this pigment. Sti-aight-chain phei~ylpropanoid compouncls related to the common aromatic amino acids were considered t o be no re plausible intermediates by Read and Vining (3), who suggested that condensation of suitable pairs of such compounds would provide a general route to the terphenylquinones. The discovery of volucrisporiil in saprophytic c~~l t u r e s of the hyplzolnycete voL~icrispora aurantiaca llasltins ( 4 ) and elucidatioll of its structure as the terphenylquinone (111) ( 5 ) have provided the first practical opportunity to test these theories. C o m p o u~~d s of this class had previously been fou~lcl only in the fruiting bodies of fungi growing in their natural environment, or in the slow-growing lichens (6).Tf . a~ira7ztiaca has now been grown in the presence of various C1l-labelled substrates ancl the incorporation of radioactivity into the piginellt examined. 'The r e s~~l t s are shown in Tables I and 11

No abstract