Ascidian tyrosine

Marine tunicates are also a source of brominated tyrosine derivatives. The colonial ascidian Aplidium sp., which was collected in Australia, yielded the novel iodinated tyrosine alkaloids 1973-1975 (1819). Collections of Botryllus sp. and Botryllus schlosseri from the Philippines and the Great Barrier Reef, respectively, have afforded botryllamides A-D (1976-1979) (1820). A Palauan ascidian Botrylloides tyreum produces several new botryllamides, including the brominated botryllamide G (1980) (1821). The simple brominated tyramines 1981 and 1982 were isolated from the New Zealand ascidian Cnemidocarpa bicornuta (1822) and an Indonesian Eudistoma sp. ascidian (1823). 

McDonald LA, Swersey JC, Ireland CM, Carroll AR, Coll JC, Bowden BF, Fairchild CR, Cornell L (1995) Botryllamides A-D, Two Brominated Tyrosine Derivatives from Styelid Ascidians of the Genus Botryllus. Tetrahedron 51 5237... 

Rao MR, Faulkner DJ (2004) Botryllamides E-H, Four New Tyrosine Derivatives from the Ascidian Botrylloides tyreum. J Nat Prod 67 1064... 

Polyandrocarpamides A-D (27-30), from the marine ascidian Polyandrocarpa sp. [31], are metabolites which appear to be derived from tyrosine (bromotyrosine, or iodotyrosine) and tryptophane. No activity was reported for the polyandrocarpamides. 

Similar metabolites which appear to be derived from tyrosine and brominated tyrosine include botryllamides A-D (31-34), which were isolated from brightly coloured styelid ascidians from the genus Botryllus collected in Fiji and in Australia [32]. Botryllamide D was reported to exhibit marginal cytotoxicity after 72 hour exposure to the human colon cancer cell line HCT 116 (IC50 17 pg/mL), but were inactive in vivo. The rubrolides, which were isolated from Riterella rubra [33] may well be derived from precursors similar to the botryllamides, however, the rubrolides are not alkaloids so have been mentioned here only for comparative purposes. 

The polyandrocarpamides combine a derivative of phe-nylethylamine with an indole nucleus, which may be halogenated. Thus, polyandrocarpamide B is one of the rare iodinated derivatives isolated from an ascidian (Lindquist and Fenical, 1990). Polyandrocarpamines A and B are also derived from tyrosine and have a 2-amino-imidazolone. No particular biological property has been mentioned for these four derivatives. 

The bastadins are a series of predominantly macrocycUc bromotyrosine derivatives, which are biogeneticaUy derivable from four bromotyrosines by the oxidative phenohc coupling of two tyramine tyrosine units cormected through an amide bond. Until now, there are four acychc, twenty cychc bastadins, and sixteen hemibastadins isolated from marine sponges and ascidians. Examples of this class of alkaloids are bastadins-1 (204) and -5 (209). 

There are a number bromotyrosine derived compounds not belonging to any of the above structure classes. Geodiamolides, a series of cyclic depsipeptides, are included in this review since they contain halogenated tyrosine. Polycitones and polydtrins are condensation products of substituted bromotyrosine molecules, isolated from ascidians, and are also included in this review. Similar structures including lamellarins are not included due to the absence of halogenation. For the same reason, polyandrocarpamides A-C (253-255), chelonin B (256), and 5-bromochelonin B (257) are included. 

Compound 199 and purealidin O (200) are two oxime-type bromotyrosine-derived metabolites containing an agmatine moiety, isolated from Psammaplysilla purea and Oceanapia sp., respectively (79,90). Alkaloids 201, 202, and 203 were iodinated tyrosine derivatives isolated from the ascidian Aplidium sp. (127). 

Polyandrocarpamides A-C (253-255), which are derived from tryptophan and tyrosine subunits, were isolated from the marine ascidian Polyandrocarpa sp. (153). Structurally related alkaloids, the chelonins, were reported from the marine sponge Chelonaplysilla sp., of which chelonin B (256) and 5-bromochelonin B (257) contain a bromotyrosine (154). 

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