Calophyllum products. IV. Papuanic and isopapuanic acids

Abstract

Papuanic acid from the bark resin of Calophyllum papuanum Lauterb. is shown to have the structure and absolute stereochemistry 29a by a combination of degradative, synthetic, and X-ray crystallographic methods. Isopapuanic acid, also present in the resin, is the C-2 epimer 3Oa. The stereochemistry and conformations of these compounds and their epimerixation and bromination products are discussed. The synthesis of a derivative of papuanic acid is described.

<b>PHLOROGLUCINOL DERIVATIVES AND FLAVONES FROM <i>HELICHRYSUM PARONYCHIOIDES</i></b>

“…Although compound 1 is herewith reported for the first time as a natural product, it is a principle building block of Calophyllum metabolites [25][26][27][28][29][30] and thus a precursor towards the total synthesis of an anti-HIV-1 compound, (±)-calanolide A [31]. The absolute configuration of 1, (2R,3R)-5,7-dihydroxy-2,3-dimethyl-4-chromanone, was inferred from the already established configuration of papuanic acid isolated from Calophyllum papuanum [28,32].…”

“…Although compound 1 is herewith reported for the first time as a natural product, it is a principle building block of Calophyllum metabolites [25][26][27][28][29][30] and thus a precursor towards the total synthesis of an anti-HIV-1 compound, (±)-calanolide A [31]. The absolute configuration of 1, (2R,3R)-5,7-dihydroxy-2,3-dimethyl-4-chromanone, was inferred from the already established configuration of papuanic acid isolated from Calophyllum papuanum [28,32]. For further proof of the structure, total synthesis of compound 1 was achieved by Friedel-Crafts acylation of phloroglucinol and tigloyl chloride with subsequent Michael Addition type reaction giving a 1:1 mixture of trans and cis products, as also reported in the synthesis of both papuanic acid [28] and (±)-calanolide A [31].…”

“…The absolute configuration of 1, (2R,3R)-5,7-dihydroxy-2,3-dimethyl-4-chromanone, was inferred from the already established configuration of papuanic acid isolated from Calophyllum papuanum [28,32]. For further proof of the structure, total synthesis of compound 1 was achieved by Friedel-Crafts acylation of phloroglucinol and tigloyl chloride with subsequent Michael Addition type reaction giving a 1:1 mixture of trans and cis products, as also reported in the synthesis of both papuanic acid [28] and (±)-calanolide A [31].…”

Daltonkins A and B, Two New Carboxyethylflavanones from the Heartwood of Dalbergia tonkinensis

“…Up until the present, not many natural compounds with side chains containing propanoic acid moiety or carboxyethyl groups have been discovered. The few reported products include derivatives of phenylpropanoic acid from the heartwood of Cordia trichotoma and a Streptomycetes strain; carboxyethylchromanones from the bark of Calophyllum papuanum and the fruit of Foeniculum vulgare ; and carboxyethylflavonoids as a biosynthetic product from Vitis vinifera leucoanthocyanidin dioxygenase . With regards to species of Dalbergia , only L‐3,4‐dihydroxyphenylalanine (L‐DOPA) had been isolated from the seeds of D. retusa and D. glabra .…”

Tandem Alkyne Hydroacylation and Oxo-Michael Addition: Diastereoselective Synthesis of 2,3-Disubstituted Chroman-4-ones and Fluorinated Derivatives

“…Reactions of salicylaldehyde with 1,2-dialkylacetylenes occur to form the corresponding 2,3-dialkylchroman-4-ones, which are found in a variety of naturally occurring chroman-4-ones, 11 in higher yields than analogous reactions of 1,2-diarylacetylenes. For example, reactions of 3-hexyne and 4-octyne with salicylaldehyde occur to form 2,3-dialkylchroman-4-ones 3g and 3h in 92% and 94% yield.…”