The natural products isolated from Lecanora gangaleoides include two depsides, atranorin (1 ) and chloroatranorin (2), two depsidones, gangaleoidin (4) and leoidin ( 5 ) , and the bisanthraquinone, skyrin (6). The constitution (5) for leoidin has been established by its transformation into the diphenyl ether (15) which was also obtained from gangaleoidin (4).Six compounds, which were all believed to be natural products, were isolated when the lichen, Lecanora gangaleoides, was first investigated by Nolan during the period 1935-1943. 1-3 Three of these natural products were identified as the depsides, atranorin ( I ) and chloroatranorin (2) and the depsidone, gangaleoidin (3). In addition, three uncharacterised compounds were also isolated which included (i) a colourless compound, C,6H,1C13010, m.p:.. 231-233 "C, (ii) a red pigment, rhodophyscin, and (111) a yellow pigment, endococcin. The constitution (3) proposed by Nolan for gangaleoidin was based upon an extensive investigation l P 3 by the Dublin group. However, much later it became clear that their structural proposal (3) for gangaleoidin required careful re-examination. The studies by Sargent, Vogel, and Elix4 and our independent investigations 5.6 established that gangaleoidin had the constitution (4). Sargent, Vogel, and Elix reported the isolation from their sample of Lecanora gangaleoides of atranorin (l), chloroatranorin (2), gangaleoidin (4), and an orange metabolite, which was not characterised but was probably identical with rhodophyscin.' We were also simultaneously examining this problem 5.6 and we now report upon our phytochemical exam i na t i o n of Lecanora gangaleoides.The lichen, Lecanora gangaleoides, which was collected in North Wales, yielded six compounds which were obviously identical with the six substances previously described by Nolan.' Atranorin (I), chloroatranorin (2) and gangaleoidin (4) were easily identified. Leoidin, C, ,H 14C1207, m.p.
231-233' C , is obviously identical with the unnamed compound, m.p. 23 1-233 "C, previously isolated by Nolan 0 CHO Me Atranor in ( 1 ) X = H Chloroatranorin ( 2 ) x = c I Skyrin ( 6 ) * We thank Mr. N. Woodhead of the Department of Botany, University College of North Wales, Bangor, for his advice regarding the location of this lichen near Dyffryn Ardudwy, Merionethshire. * We thank Dr. C. A. Wachtmeister, Institutionen for organisk Kemi, Kungl. Universitet J. Stockholm, for his kind assistance in providing authentic samples of lichen metabolites. t We thank Professor S. Shibata, Meiji College of Pharmacy, Tokyo, for a sample of ( + )-skyrin.
