The synthesis of the alkaloids (±)-fumaritine and fumariline

Abstract

Prior to the establishment of formula (II) for fumaritine, an alkaloid from Fumaria officinalis L., we prepared 1,2,3,4-tetrahydro-7-methoxy-2-methyl-6′,7′-methylenedioxyisoquinoline-1-spiro-2′-indane-1′,6-diol (I) from the known N-nor-ketone (IV). Since the product (I) was not identical with fumaritine, we synthesised the 7-hydroxy-6-methoxy-isomer (II) from the corresponding 6,7-dihydroxy-N-nor-ketone (VI) in several steps; this product (II) was identical with the alkaloid. Another minor alkaloid from the same plant, fumariline, was also prepared from compound (VI). The imino-group was protected by forming an imidazolidinone ring with methyl isocyanate. Methylenation of the dihydroxy-system followed by treatment with lithium aluminium hydride to remove the imidazolidinone ring gave 1,2,3,4-tetrahydro-6,7:6′,7′-bismethylenedioxyisoquinoline-1-spiro-2′-indan-1′-one (X), which on N-methylation gave fumariline (XI).