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Phytotoxic Compounds produced by Fusarium equiseti. Part 11.l The Chemistry of Diacetoxyscirpenol By A. W. Dawkins Diacetoxyscirpenol, the principal toxic metabolic product of Fusarium scirpi, is shown to possess structure ( I a ) by transformation to a derivative ( I I I d ) of verrucarol.

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2203 439. Griseofulvin. Part XVI." Synthesis of Compounds related to &iswfulvin.

The structures of the 3.4-seco-products from the oxidative fission of trichothecan-3a,4~,15-triols by activated manganese dioxide have been elucidated.THE trans-ap-glycol system in 12,13-epoxytrichothec-9-en-3a,4@,15-triol ( I ; R = R' = H) (scirpentriol: for nomenclature see ref.2) and in the 15-monoacetate (I; R = Ac, R' = H) was shown to be stable to peri-odate314 and to lead tetra-acetate in acetic acid: but was cleaved by the latter reagent in chloroform to give, from the triol (I; R = R' = H), in fair yield, an amorphous hemiacetal (VIII; R = H), characterised as the acetate (VIII; R = Ac). The hemiacetal (VIII; R = H) was oxidised further by chromic oxide in dimethylformamide in the presence of sulphuric acid to an amorphous 8-lactone which was considered to have the structure (VII). Ring c of the trichothecan-3,4-diol 4 €3.

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The synthesis is described of grisan and coumaran-3-one spirocyclopentane analogues of some griseofulvin derivatives, and of racemates of the griseofulvin degradation products, (Z,d) -7-chloro-4 : 6-dimethoxy-2'-methylgrisan-%one * (11) and (d,d)-7-chloro-4 : 6-dimethoxy-2'-methylgrisan-3 : 4'-dione (111).THE preceding paper described a synthesis of the racemate of (Z,d)-?-chloro-4 : 6-dimethoxy-2'-methylgrisan-3-one * (11), the racemate of a product obtained from (Z,d)-griseofulvin (I). In the present paper details are given of a second route3 which led to the synthesis of the racemates of the (Z,d)-ketone (11) and of (d,d)-7-chloro-4 : 6dimethoxy-2'-methyl@an-3 : 4'-dione (111). This route was based on reports * s 5 that the usnolic acid analogue (IV; R = R' = Me) obtained by ring closure of the keto-ester (V; R = R' = Me) with sulphuric acid4y5S6 was a spiran rather than a dihydrodibenzofuran derivative. Ozonolysis of the ester (IV; R = R' = Me) gave formaldehyde and a compound shown to be a coumaranone ester (VI; R = R' = Me, R ' = C0,Et) by spectroscopy and oxidation to a salicylic acid. Since grisans containing a C-methyl group in the correct position for derivatives of griseofulvin might be obtained by this route, it was further investigated. Me0 @r&o " . Me0 Me0 \ Me M e 0 \ CI ' ov M e O U r D ' CI Me CI (1) (11) (111) *COMe R Me R" (i) The synthesis6 of the ester (IV; R = OMe, R' = H) was extended to give the spiran (VII). The orientation of the formyl group in the intermediate aldehyde (VIII; R = R' = H, R" = CHO), previously6 based on a mixed decomposition point of the corresponding acid (VIII; R = R' = H, R" = CO,H), was confirmed by comparison of its ethyl ester with an authentic specimen of ethyl 6-methoxy-3-methylcoumaranone-2carboxylate. The keto-ester (V; R = OMe, R = H) obtained6 from the above aldehyde was cyclised with sulphuric acid to the spiran (IV; R = OMe, R' = H) either directly6 or through its copper chelate. The spiran showed strong absorption at 328 mp (log c 3.98) , assumed to be due to the exocyclic methylene group conjugated with the aromatic ring. In this it resembled the analogue (IV; R = R' = Me). The dihydro-derivative (IX) showed only weak absorption (C=C-C=O, R band) at 321 mp. Ozonolysis of the ester (IV; R = OMe, R' = H) gave formaldehyde and the coumaranone ester (VI; R = OMe, R' = H, R" = CO,Et), which no longer showed absorption at 1649 cm.-l (=CHJ but * Concerning (Z,d) see footnote, p. 2203, and ref. 2. Part XVI, Dawkins and Mulholland, preceding paper.