L. Merlini

Screening of the genus Cercospora for secondary metabolites

Abstract Screening of 61 species of Cercospora grown on a potato-agar medium showed the presence of the phytotoxin cercosporin in 24 of them, and of dothistromin in 8. Some strains of C. beticola produce a yellow phytotoxin (CBT). The new metabolites cercosporin esters, ligustrone A, B, C, taiwapyrone, 3-methoxy-2,5,7-trihydroxy-1,4-naphthaquinone, cis -4,6-dihydroxymellein and ( − )-11-acetyldehydrocurvularin were isolated besides the known cynodontin, ( − )-dehydrocurvularin, (+ )-mellein and cis -3 S ,4 S -4-hydroxymellein.

Synthesis of d,l-cannabichromene, franklinone and other natural chromenes

Abstract The natural chromenes d,l -cannabichromene, franklinone, alloevodionol, evodionol methyl ether and the trimethy ether of flemingin C were synthesized by cyclodehydrogenation of the corresponding isoprenylphenols with 2,3-dichloro-5,6-dicyanobenzoquinone (DDQ) or via the chromanes and dehydrogenation with DDQ. The biogenetical interest of this route is emphasized.

Reaction of ortho alkenyl- and alkylphenols with 2,3-dichloro-5,6-dicyanobenzoquinone (DDQ): Syntheses of 2,2-dialkylchromenes

Abstract The reaction of γ,γ-disubstituted ortho α,β-alkenyl, β,γ-alkenyl and alkylphenols with 2,3-dichloro-5,6-dicyanobenzoquinone (DDQ) in boiling C6H6 gave 2,2-dialkylchrom-3-enes. Lack of substitution at γ position usually inhibited the reaction. Thymol and 2,6-diisopropylphenol gave nuclear coupling products, whereas the spiropyran IV was obtained from 2-propenylphenol. The remarkable influence of the solvent on the products of the reaction is shown in the case of 2-isoamyl-5-heptylphenol. The possible mechanisms of the reaction are discussed.

Metabolites of Cercospora. Taiwapyrone, an α-pyrone of unusual structure from Cercospora taiwanensis

Abstract (+)-Mellein ( 1 ), cis-3 S ,4 S -4-hydroxymellein ( 3 ), and taiwapyrone ( 4 ), a new α-pyrone, have been isolated from the mycelium of Cercospora taiwanensis , grown on potato-agar. The structure and absolute configuration of ( 3 ) and ( 4 ) have been elucidated.

Indole alkaloids from gambir structure of bambirtannine, oxogambirtannine and dihydrogambirtannine

Abstract On the basis of chemical and spectral evidence, the structures I, II and III were assigned to gambirtanine, dihydrogambirtannine and oxogambirtannine, three new indole alkaloids extracted from the tannin Gambir. The phenol betaine IV (neooxygambirtannine) was obtained during the workup of the extract.

The structure of roxburghines A–E, new indole alkaloids from an Uncaria Sp☆

Abstract The structural elucidation of roxburghines A–E, new diastereoisomeric indole alkaloids C 31 H 32 N 4 O 2 , isolated from the leaves and stems of an Uncaria Sp., is reported. The derivation of the skeleton ( 4 ) from two tryptamine and one monoterpenoid C 10 units is consistent with the current biogenetic theory. Tetrahydroalstonine, one isomer, and dihydrocorynantheine were also isolated.

Dothistromin and 2-epidothistromin from Cercospora smilacis

Abstract Examination of a strain of Cercospora smilacis Thum grown on potato-agar medium showed the presence of the known phytotoxin dothistromin together with the new 2-epidothistromin. Mutual conversion by epimerization at C-2 occurred during derivatization.

Structure and synthesis of new natural heteroyohimbine N-oxides

Abstract Natural 4,R-akuammigine N-oxide, (1) 4,S-akuammigine N-oxide, (2) and 4,R-tetrahydroalstonine N-oxide (3) have been isolated from species of Uncaria. (Rubiaceae). Their stereochemistry has been established from NMR spectra. Synthesis of 1,2,3 and of 4,R-ajmalicine N-oxide and 4,R-3-isoajmalicine N-oxide by peracid oxidation of the bases is described.

New chromenochalcones from Flemingia

Abstract 2-Methyl-2-(4′-methylpent-3′-enyl)-5,8-dihydroxy-6-(4-hydroxycinnamoyl)-chromene (flemingin- D ) has been isolated from inflorescences of Flemingia congesta , together with the known flemingin- C and two other chalcones. These (flemingin- E and - F ) are allylic alcohols which differ from flemingin- D by an additional OH group in the side chain. Photooxidation of model 2-methyl-2-(4′-methylpent-3′-enyl)-chromenes gave pairs of allylic alcohols with the same structural feature. The known flemingin- A , - B , - C and homoflemingins have been isolated from F. grahamiana , and another new chalcone from F. bracteata .

Hashish : Synthesis of (+)-Δ4-tetrahydrocannabinol

Abstract Alkylation of olivetol with p -menth-4-en-3,8-diol ( 3 ) afforded Δ 4 -tetrahydrocannabinol, an unknown isomer of the hashish active constituent Δ 1 -THC, together with the “abnormal” isomer. The attack of olivetol onto the positions 3 and 5 and resp. 3 and 8 of ( 3 ) yielded derivatives of 2,6-methano-2H,1-benzoxocin-7-ol and new 2,3,4,4a-tetrahydroxanthenes.