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1. When [1:2 -14C2]ethanolamine, serine, L-[3H]serine or D-[3H]serine was administered orally to earthworms, serine ethanolamine phosphodiester and lombricine were found to be radioactively labelled.2. For each of the precursors the specific radioactivity of serine ethanolamine phosphodiester was greater than that of lombricine in both muscle and gut tissue.3. The specific radioactivity of serine ethanolamine phosphodiester and lombricine was greater in gut than in muscle. With [1:2-4C2]ethanolamine most of the radioactivity of muscle lombricine was in the guanidinoethanol portion of the molecule, whereas with DL-[3-L4C]serine most of the radioactivity was in the serine portion.5. When L-[amidino-14C]arginine was given, there was negligible radioactivity in serine ethanolamine phosphodiester and considerable radioactivity in lombricine, almost all of which was in the guanidinoethanol portion of the molecule.6. These findings suggest that serine ethanolamine phosphodiester is the precursor of lombricine in the earthworm and that the amidino group is derived from arginine by the transamidinasecatalysed transfer of the amidino group to serine ethanolamine phosphodiester.We are indebted to Dr D. I. Magrath and Mrs I. M. Beatty for a sample of synthetic SEP, to Dr R. Norris for advice about the earthworms and to Mr P. Allen for technical assistance. 126, 446. amino acid oxidase were purchased from * Salters' Student. RIBITOL TEICHOIC ACID FROM BACILLUS SUBTILIS L. Light and Co. Ltd., Colnbrook, Bucks. B. &subtilis was grown from a culture provided by Dr M. R. J. Salton.

The structures of cytochalasins A and 6, metabolites of Helminthosporium demarioideum showing novel effects on mammalian cells, have been determined. Cytochalasin B is identical with phomin. (7)-a-Methyladipic acid is shown to have the R-configuration contrary to a previous assignment; the absolute configurations of the Nupheus alkaloids therefore require revision.OUR interest in the fungus Helminthosporium dematioideum arose from the observation1 that the aqueous media on which it had grown produced unusual morphological effects on the hyphae of other fungi. A follow-up of this observation led to the isolation of two related compounds, one of which was responsible for the effects. Subsequently, both compounds were found to produce novel effects on mammalian cells in tissue culture and the same effects were observed to be produced by filtrates from fermentations of other fungi, from one of which, Metarrhizium anisopliae, we have isolated a second pair of biologically active compounds related structurally to those from H . dematioidezcm. The name " cytochalasins " (cytos = cell, chalasis = relaxation) has been proposed for this class of compounds, those from H . dematioideum being cytochalasin A, which is responsible for the effects on fungal hyphae, and cytochalasin B; those from M . anisopliae are cytochalasins C and D.* This report describes work, a brief account of which has a ~p e a r e d , ~ which permits us to assign structures (Ia) and (Ib), respectively, to cytochalasins A and B.The relationship (+unsaturated ketone and allylic alcohol) between cytochalasin A, CzgHsNO,, and cytochalasin B, &H,,N05, could be deduced from their n.m.r. spectra (Table 1). In that of cytochalasin A, 2-H and 3-H give rise to an AB quartet, while in cytochalasin B 3-H is further coupled (J = 6 c./sec.) to a proton (4-H), not present in cytochalasin A, whose signal appears at T . The relationship was confirmed by oxidation of cytochalasin B to cytochalasin A with manganese dioxide. The trans-configuration of the 2,3-double bond follows from the value of Jz,3 and is supported by the fact that irradiation of cytochalasin B with ultraviolet light causes isomerisation of the double bond to the cis-configuration, with the expected fall in value of Jz,3 to 12 c./sec.Reduction of cytochalasin B with an excess of sodium borohydride gives a dihydro-compound (11) in which the 2,3-double bond has been reduced (no AB quartet in the n.m.r. spectrum of (11), signal due to 4-H shifted upfield to T 6.2). Alkaline hydrolysis of the dihydrocompound gives the hydroxy-acid (IIIa) which on treatment with acid gives the y-lactone (IVa) (vmx. 1772 cm.-l), isomeric with the dihydro-compound. This reaction sequence shows that, (i) the 2,3-double * Cytochalasins A and B are the subject of U.K. Patent Appln. No. 1,060,511; cytochalasins C and D are the subject of U.K. Patent Appln. No. 4182/66. * We are indebted t o Professor Tamm for permitting us t o see his manuscript before publication.

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prostatic phosphomonoesterase. The phosphodiester (V) was hydrolysed with alkali to glycerol and its monophosphates. It follows that the teichoic acid is a polymer in which glycerol residues are joined through phosphodiester linkages at positions 1 and 3 in the glycerol units. 4. The alanine from the polymer is readily oxidized with a D-amino acid oxidase, and thus has the D-configuration. 5. Alanine is joined to the polymer through ester linkages at the 2-position of each glycerol residue. The structure (VI) is assigned to this intracellular teichoic acid. 6. The alanine ester groups are highly reactive towards alkali and amines. They react with hydroxylamine at about the same rate as do amino acids in combination with ribonucleic acid. We thank the Medical Research Council, the Rockefeller Foundation and the Nuffield Foundation for financial support.

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