The alkaloids of perennial rye-grass (Lolium perenne L.). Part IV. Isolation of a new base, perlolyrine; the crystal structure of its hydrobromide dihydrate, and the synthesis of the base

Abstract

A new alkaloid, perlolyrine, 1-(5-hydroxymethyl-2-furyl)-9H-pyrido[3,4-b]indole (6b), has been isolated from Lolium perenne L. (Graminae). The structure of the base was revealed by an X-ray analysis of its hydrobromide dihydrate C₁₆H₁₂N₂O₂,HBr,2H₂O (space group P, a= 7·81, b= 10·55, c= 10·55 Å, α= 79·2 β= 72·9, γ= 78·8°), by use of the heavy-atom method, assisted by spectroscopic data. The final value of R over 2360 reflections is 0·129; an attempt to refine the structure in space group P1 failed. The alkaloid has been synthesised from tryptophan and 5-acetoxymethyl-2-formylfuran. The 3,4-dihydro- and 1,2,3,4-tetrahydro-derivatives have also been synthesised, starting from tryptamine. The ways in which perlolyrine and its reduced derivatives break up on electron impact are discussed. Perlolyrine is shown to be present in the dried grass, and is not an artefact of the working-up process.