that the red fruits of Riuinia hurnilis L. contain, besides betanin and isobetanin, a red-violet pigment (rivinianin). In the present study the rivinianin has been shown to be betanin 3'-sulphate.Rivinianin was isolated from aqueous extracts of fruits by preparative electrophoresis. Since the pigment (λmax 253 541 nm; mobility relative to betanin 1.78 at pH 2.4 and 1.34 at pH 4.5) gave on complete acid hydrolysis a mixture of betanidin and isobetanidin, it is a betanidin derivative; the hydrolysate also contained glucose identified by PC (six solvents) and sulphate identified via BaCl2. Alkaline hydrolysis of rivinianin in the absence of oxygen gave, besides sulfuric acid, a mixture of betanin and isobetanin identified by paper electophoresis, analytical column chromatography on polyamide and treatment with fi-glucosidase which gave glucose and a mixture of betanidin and isobetanidin [3,4]. Since diazomethane methylation of rivinianin followed byalkali fusion gave 5-hydroxy-6-methoxyindole-2 carboxylic acid, it was inferred that the hydroxyl group at position 6 of the aglycone is free. In order to ascertain the position of the SO3- group in the glucose residue, rivinianin was treated with Me1 in HCONMe2 in the presence of AgO. The permethylated product on acid hydrolysis gave 2,4,6-tri-O-methyl-D-glucose; from this it follows that only one SO3- group is present in the molecule and this is linked to the hydroxyl group at position 3' of the glucose residue. The Malaysian tree Adina rubescens has yielded several indole alkaloids with novel structural features. In particular, a unique group containing a carboxyl function constituted the first representatives of a hitherto unknown series with standard monoterpenoid C10 units but derived directly from tryptophan rather than the ubiquitous tryptamine [l-3]. We now report the discovery of a second tetracyclic carboxy Corynanthe alkaloid -anhydroadirubine, for which structure la is suggested.Chromatography of a methanolic extract of the heartwood from A. rubescens on ion exchange resins, followed by gel permeation afforded an amino-acid concentrate. After methylation and preparative TLC a small amount of an amorphous alkaloid C21H28O4N2 [α]; -28° was obtained. Its UV spectrum indicated an indolic chromophore, confirmed by NMR signals for four aromatic protons in the τ 25-3-l region and an indolic NH at τ 218, with a corresponding IR band at 3480 cm-1. Two IR carbonyl absorptions at 1745 and 1720 cm-1 and a pair of methoxyl singlets in the NMR spectrum at τ 6.20 and 6.23 suggested two methyl esters, one of which waspossibly conjugated with an olefinic methylene group evident from an IR peak at 1630 cm-1 and two one-proton singlets at 7 3.70 and 4.35. A distorted 3-proton triplet at 5 9.12 established an ethyl group.Dominant mass spectral fragments (see Scheme 1) at m/r 337 (M-CO2Me), 335 (M-CO2Me-2H), 242 and 168 were characteristic of a tetrahydro-flcarboline substituted at C-5 by a carbomethoxy group, and immediately reminiscent of methyl adirubine (2b Cl]. The resemblance extended to substantial M-l, 195, 182 and 156 ions consistent with a fourth ring linked to C-3 and N-4 in the unknown alkaloid also. However, one major difference was the lack of any substantial ion derived by cleavage of the 15-16 bond and loss of the 'C3' unit which was so apparent with methyl adirubine, e.g. W/P 269.Confirmation of the olefinic bond was obtained by catalytic hydrogenation to a mixture of two isomeric dihydro-derivatives. In addition to the above features the mass spectra now exhibited ions at m/e 269 (M-87) etc., attributable to a Ii-16 cleavage and loss of MeO,C-CH-Me. From this behaviour it could be deduced that the original compound must have contained a conjugated ester moiety Me02C-C'6 = CH2 where (i) cleavage of the bond adjacent to the sp [2] hybridized C-16 would not be favoured, and (ii) hydrogenation would generate a new chiral centre at C-16, and thus two products. At this stage the most probably gross structure of the alkaloid was that of methyl anhydroadirubine (lb). Since the CD spectrum showed a positive Cotton efiect between 250 and 300 nm, the absolute configuration at C-3 must be x (S), and trM/rs-yuinolizidine IR bands in the 2700.-2800 cm-1 region indicated that H-3 was cis to H-15 which thus had the expected x configuration.In view of this stereochemical correspondence at two centres. a chemical correlation with adirubine seemed feasible. Accordingly. elimination of acetic acid from methyl adirubine acetate (2~) with refluxing methanolic sodium methoxide gave methyl anhydroadirubinc (lb) identical with the isolated alkaloid by IR, NMR, CD spectra and TLC in several systems. Further, since methyl adirubine was recovered unchanged from the reaction, no epimerisation of H-5 had occurred. indicating that the 5-carbomethoxy group was already in the more stable equatorial orientation and hence /I. This means that H-5 ir, adirubine and its derivatives have the x (S) configuration in agreement with a derivation from r_-tryptophan. Hence the isolated methyl ester is represented by structure 1 b, the naturally occurring carboxy alkaloid presumably being anhydroadirubinc (la) by analogy with adirubinc (2a). Plant. Palicourea alpina (SW.) DC. Source. Newcastle, St. Andrew, Jamaica, collected in October 1970 (Herbarium No. 27,179, Botany Department, University of the West Indies). Previous work. Plant material from Hardwar Gap, St. Andrew collected in July 1973 was shown to contain vomifoliol [ 11, indole alkaloids palinine, palidimine and harman [2].Present work. Stems and leaves were dried and powdered (150 g). Extraction with 2% tartaric acid followed by the usual work up for basic material[l] yielded 0.275 g of crude material. PLC on silica plates using CHCL-MeOH (1: 1) afforded 12 mg of a chromatographically homogeneous solid which had identical physical properties (UV, IR[3], NMR[4] to calycanthine. High resolution MS showed that the base peak was the parent ion (m/e 346.2113; Calculated for C22H26N4, 346.2157) and the fragmentation pattern observed was very similar to that reported earlier for calycanthine [5].Calycanthine has previously been shown to be the principal poisonous constituent of Calycan thus glaucus Willd.[6] and was also reported from C. floridus L. [7] and C. occidentalis Hook. and Am. [8] (Calycanthaceae). Chimonanthus praecox (L.) Link ( = Meratia praecox Rehder and Wilson) Calycanthaceae[9] and Bhesa archboldiana (Merr. and Perry) Ding Hou(Celastraceae) [lo] have also been shown to contain this alkaloid, but this is the first report of its isolation from the Rubiaceae. It is noteworthy that specimens of Palicourea alpina growing at Hardwar Gap, only 2 km from the location of the plants used in this study, did not yield this alkaloid, but other indole types were shown to be present [2].