REACTIONS OF NITRILE CYCLIZATION .27. SYNTHESIS OF ANNELATED PYRIDINES AND THIENOPYRIDINES BASED ON PREGNA-5,16-DIEN-3-BETA-OL-20-ONE ACETATE AND METHYLENE-ACTIVE NITRILES - MOLECULAR AND CRYSTAL-STRUCTURE OF 3'-AMINO-6'-METHYL-2'-CYANO-3-BETA-HYDROXYANDROST-5-ENO[16,17-D]THIENO[2',3'-B]PYRIDINE