Victor I. Hugo

A HIGH YIELDING SYNTHESIS OF RACEMIC HONGCONIN

Racemic hongconin 1 has been synthesized from adduct 2 formed by reaction between 1-methoxycyclohexa-1,4-diene and benzoquinone. The synthetic strategy includes Fries and Claisen rearrangements, base and cerium(IV) initiated pyran ring formation, C-4 pyran ring hydroxylation and silver(II) mediated oxidation.

Naphtho[2,3-c]pyran-5,10-quinones. Syntheses of the racemates of quinone A, quinone A′, and deoxyquinone A dimethyl ethers of 7-methoxyeleutherin, and of isoeleutherin

Treatment of 3-(1-hydroxyethyl)-1,4,5,7-tetrarmethoxy-2-prop-2-enylnaphthalene (33) with potassium t-butoxide in dimethylformamide under nitrogen for a short time gave a high yield of trans-3,4-dihydro-5,7,9,10-tetramethoxy-1,3-dimethyl-1H-naphtho[2,3-c]pyran (41). This compound, with the same base and solvent, but in air, afforded a mixture comprising its cis-epimer (42), together with the two possible 4-hydroxy derivatives, namely (35) and (38). Silver(II) oxide oxidation of compounds (35), (38), (41), and (42) gave, respectively, the dimethyl ethers of quinone A, quinone A′, and deoxyquinone A, and also 7-methoxyeleutherin.

Base-induced cyclisations of naphthalenes into naphtho[2,3-c]pyrans. Application to stereospecific syntheses of (±)-isoeleutherin and (±)-deoxyquinone a dimethyl ether

2-(Alk-2-enyl)-3-(1-hydroxyalkyl)-1,4-dimethoxynaphthalenes are cyclised and then oxidised to naphtho[2,3-c]pyran-5,10-quinones which are naturally occurring quinones or their derivatives.

Synthesis of 1,1,3-Trisubstituted Naphtho[2,3-c]-pyranquinones

Abstract Convenient syntheses for two 1,1,3-trisubstituted naphtho[2,3-c]pyranquinones have been developed. Alkylation of acetyl and trifluoroacetyl naphthoquinones afforded the target pyranquinones in a one-pot reaction.

Synthesis of 1,5-Dimethoxy-4-naphthol and 2-Allyl-5-methoxy-1,4-Naphthoquinone A New Approach

Abstract Convenient syntheses for 1,5-dimethoxy-4-naphthol and 2-allyl-5-methoxy-1,4-naphthoquinone have been developed. A key step in the formation of the title compounds involved methylation or allylation of an intermediate Diels-Alder adduct.

Synthesis of 3-Acetyl-5-methoxy-1,4-naphthoquinone. A New Approach

Abstract A new and efficient synthesis for 3-acetyl-5-methoxy-1,4-naphthoquinone has been developed. The synthesis involves inter alia pyrolysis of an acetylated Diels-Alder adduct and a regiospecific Fries rearrangement reaction.

Bromination Products of 2‐Substituted 5,7‐Dimethoxy‐4‐Naphthols

Abstract Bromination in acetic acid is favored at C‐8 in 5,7‐dimethoxy‐4‐naphthol when the C‐2 substituent is methyl carboxylate, whereas C‐1 is favored when the C‐2 substituent is either acetoxymethylene or methyl.

Synthesis of Some C‐4 Hydroxybenzo[c]pyrans: A New Approach

Abstract A new synthetic approach to the synthesis of some epimeric C‐4‐hydroxy‐benzo[c]pyrans is described. A key step in their formation is stereoisomerisation of a nonconjugated ortho alkenylphenylketone and ‐ester using palladium bisacetonitrile [bisacetonitriledichloropalladium(II)] to give the corresponding conjugated E stereoisomers which cyclize on treatment with meta‐chloroperbenzoic acid (m‐CPBA) to afford the target compounds.

Synthesis of a Naphtho[2,3-c]pyranone as a Model for the Construction of the Lactone Ring

Abstract A model route to an oxygenated naphtho[2,3-c]pyranone is described. It is envisaged that this route would be generally applicable to the synthesis of higher oxygenated naphtho[2,3-c]pyranones by virtue of the nature of the conditions and reagents used.

The synthesis of some naphtho[2,3-b]pyran-5,10-quinones as preliminary models for biological evaluations

Abstract Naphtho[2,3-b]pyran-5,10-quinones related to the known antibiotic, erythrostominone 5, have been synthesized and demonstrate that biological activity is a function of the pyran ring as well as substituents at C-2 and C-4.