Preparation of eumelanin-related metabolites 5,6-dihydroxyindole, 5,6-dihydroxyindole-2-carboxylic acid, and their O-methyl derivatives

5,6-Dihydroxyindole (5,6DHI) and 5,6-dihydroxyindole-2-carboxylic acid (5,6DHI2C) are ultimate precursors of the black melanin, eumelanin. These indolic metabolites and their O-methyl derivatives are excreted in urine of melanoma patients at high levels and of healthy persons at low levels. We describe here a simplified procedure for preparing milligram to subgram quantities of 5,6DHI and 5,6DHI2C and their O-methyl derivatives. Dopachrome generated in situ by ferricyanide oxidation of dopa at pH 6.5 underwent spontaneous decarboxylation to give 5,6DHI in 40% isolation yield, while treatment of dopachrome with alkali at pH 13 afforded 5,6DHI2C in 38% isolation yield. Two isomeric O-methyl derivatives of 5,6DHI were prepared by treatment with diazomethane, while those of 5,6DHI2C were prepared by treatment with diazomethane followed by alkaline hydrolysis of the methyl esters. 5,6DHI and 6-hydroxy-5-methoxyindole were also obtained by heating the corresponding carboxylic acids in decalin. 5-Hydroxy-6-methoxyindole and 6-hydroxy-5-methoxyindole-2-carboxylic acid could also be prepared by debenzylation of the commercially available O-benzyl derivatives.     

New sharks of the genus Abdounia (Carcharhiniformes: Carcharhinidae) from the Upper Eocene of the Trans-Ural Region

Two new species of carcharhinid sharks from the Late Eocene deposits (Tavda Formation) of the southern Trans-Urals, Abdounia vassilyevae sp. nov., previously determined as A. aff. beaugei, and A. lata sp. nov., are described. To date, up to five Priabonian species of Abdounia have been recorded. New finds supplement the data on diversity, evolution, and paleobiogeography of Abdounia.     

Non‐pollinating cheater wasps benefit from seasonally poor performance of the mutualistic pollinating wasps at the northern limit of the range of Ficus microcarpa

1. Species interactions in tightly bound ecological mutualisms often feature highly specialised species' roles in which competitive exclusion may preclude multi‐species coexistence. Among the 800 fig (Ficus) species, it was originally considered that each was pollinated by their own wasp (Agaonidae). However, recent investigations show that this ‘one‐to‐one’ rule often breaks down, as fig species regularly host multiple agaonids but in ways suggesting that competitive processes still mediate biodiversity outcomes. 2. A phenological survey was conducted of the fig–fig wasp pair, Ficus microcarpa and its associated pollinating wasp, alongside its sister species, the cheating wasp, in Xishuangbanna, China. 3. Reproductive output underwent extreme seasonal variation. Seed and pollinator production fell markedly during cooler, drier months, although high levels of fig production continued. However, this resource was predominantly utilised by the cheater species, which offers no pollination services. Pollinators and cheaters rarely co‐occur, suggesting that temporal coexistence is constrained by competition for access to figs. 4. The overall findings indicate periodic rearrangements of mutualism dynamics, probably resulting from a strongly seasonal environment. Sympatric co‐occurrence may result from a window of opportunity for a functionally divergent agaonid, potentially due to constraints on the main pollinator in adapting to variable year‐round conditions that prevent competitive exclusion.