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Reaction o f 4-hydroxy-3-prenylquinolin-2(l H)one (5 a) with iodine and silver acetate gave a iodopyranoquinoline (6 a), which was then converted into the alkaloids khaplofoline (1) and ribalinine (2). Reaction o f 5 a with iodine and mercuric oxide afforded a mixture o f 6a and its angular isomer 7 a; the coversion o f latter into flindersine (10) is described.Pyranoquinoline alkaloids, which possess inter esting pharmacological properties are known [1,2] to occur in the plant family Rutaceae. The alka loids, khaplofoline (1) and ribalinine (2), isolated respectively from Haplophyllum foliosum (Vved) [3] and Balfourodendron riedelianum [4], members of the rutaceae, are structurally proven to be of pyrano [2,3-b]quinoline systems. Several reports have appeared in the literature for the synthesis of 1 [3,5-9] and 2 [10-12], but the yields of 1 and 2 in these attem pts were not quite appreciable and are often attended by the form ation of their isomeric products. 0 R2 1: R1 = R2 = H 2 : R1 = CH3; R2 = OH I R1In this com m unication, we wish to present an al ternative but elegant methodology for deriving the titled alkaloids from 5, which in turn was prepared [13] from 4-hydroxyquinolin-2(l H)one 3. Reac tion of 5 a with iodine, in the presence of silver ace tate in glacial acetic acid at room tem perature gave a single product (m .p. 176-177 °C) in 80% yield. It was identified to be 3-iodo-3,4-dihydro-5-oxo-2,2-dimethyl-2H-pyrano[2,3-b]quionoline (6a). In its IR spectrum two bands at 3420 cm " 1 and 1620 cm -1 were ascribable to a N H stretching and a 4-quinolinone [14] moiety respectively. In its 'H N M R spectrum; the six proton singlet at S 1.58 ppm was characteristic of a gem-dimethyl group, two double doublets with J = 17.4 and 6.6 Hz and * Reprint requests to Dr. K. J. Rajendra Prasad.Verlag der Zeitschrift für Naturforschung. D-W -7400 Tübingen 0 9 3 2 -0 7 7 6 /9 2 /0 7 0 0 -1 0 1 6 /$ 01.00/0 a single proton triplet at S 4.68 ppm were ascriba ble to methylene and methine protons forming ABX system and a singlet at ö 11.83 ppm assigna ble to N H proton. The molecular ion peak (M +) at mle: 355 (55%) in its mass spectrum and elemental analysis C 47.30, H 4.05 and I 35.80% are well agreed to the molecular formula C 14H 14N 0 2I. Thus we realized the preparation of iodopyrano quinoline in high yield and it has proven to be a utility in heterocyclic synthesis. 6 a on alkaline hy drolysis using 0. 1% aqueous sodium hydroxide yielded 3-hydroxykhaplofoline (8); which on heat ing with methyl iodide furnished the alkaloid ribal inine 2 [4] in 90% yield. W ith the view to adducing further attestation of the iodopyranoquinoline structure assigned for the product 6 a, it was dehydroiodinated by refluxing in pyridine to chromenoquinoline 9. F urther reduction of 9 with H 2, P d -C (5 )% gave the alkaloid khaplofoline (1), which was confirmed with authentic sample [3] (m.p. CoTLC, undepressed m.m.p., superimposable IR spectra) (Scheme 1).Similar treatm ent when extended to 6-methyl-4-hydroxy-3-prenylquinolin-2(l H)one (5...

and B. S. THYAGARAJAN.Condensation of ethyl 2-pyridylacetate with diethyl methoxymethylmalonate yielded diethyl a-ethoxycarbonyl-a'-2-pyridylglutarate (11), but attempts to use the derived amide or triol for synthesis of cytisine were unsuccessful. Condensation of diethyl a-cyano-P-ethoxyacryIate with ethyl 2-pyridylacetate did not yield the expected glutaconic acid derivative. Condensation of ethyl 5-cyano-2-methylnicotinate with diethyl ethoxymethylenemalonate yielded 7 -cyan0 -3 : 9diethoxycarbonylquinolizin -4one, which on reduction of the cyano-group, decarboxylstion, hydrolysis, and re-esterscation yielded 7-aminomethyl-9-ethoxycarbonylquinolizin-4one. Reduction with lithium aluminium hydride followed by selective reduction of one ring and cyclisation afforded (-J-)-cytisine.