Total synthesis of montanine-type Amaryllidaceae alkaloids, which possess a 5,11-methanomorphanthridine ring system, through cyclization with sodium bis(2-methoxyethoxy)aluminum hydride (SMEAH): the first stereoselective total syntheses of (.+-.)-montanine, (.+-.)-coccinine, (.+-.)-O-acetylmontanine, (.+-.)-pancracine, and (.+-.)-brunsvigine