Novel 5,6-Dihydropyrrolo[2,1-a]isoquinolines as Scaffolds for Synthesis of Lamellarin Analogues

Scheme 1

Reagents and conditions: (i) BnCl, K₂CO₃, EtOH, reflux, 5 h, 94%; (ii) CH₃NO₂, NH₄OAc, AcOH, reflux, 4 h, 80.5%; (iii) LiAlH₄, THF, reflux, 6 h, 84.9%; (iv) CH₃COCl, Et₃N, CH₂Cl₂, 0°C, 2 h, 4a: 81.9%, 4b: 90.7%; (v) POCl₃, CH₂Cl₂, reflux, 3 h, 5a: 80.0%, 5b: 83.6%; (vi) 2-halogen-1-(2,4,5-trimethoxyphenyl)ethanone, CH₃CN, K₂CO₃, reflux, 20 h, I: 74.7%, II: 72.6%.