1-hydroxy-3-{[2-(1,1-dimethylallyl)-indol-3-yl]methyl}-6H,7H,8H-5lambda(5)-pyrrolo[1,2-a]pyrazine + AH2 => (S)-3-{[2-(1,1-dimethylallyl)-indol-3-yl]methyl}-6,7,8,8a-tetrahydropyrrolo[1,2-a]pyrazin-1-one + A + H(+)