ONE-POT PREPARATION OF QUINOLIZIDIN-2-ONE AND INDOLIZIDIN-7-ONE RING-SYSTEMS - CONCISE TOTAL SYNTHESES OF (+/-)-MYRTINE,(+/-)-LASUBINE-II, AND (-)-INDOLIZIDINE 223AB

highly efficient approach to the quinolizidine alkaloids (+/-)-myrtine (4) and (+/-)-lasubine II (5) and to the indolizidine alkaloid (-)-indolizidine 223AB (6) is described. The preparation of quinolizidin-2-ones 4/4a and 11b/12b and indolizidin-7-ones 16/17 is based on the addition of 2-((trimethylsilyl)oxy) 1,3-dienes 2a,b and 2c to cyclic N-acyliminium ions 10 and 15, respectively. It encompasses five chemical transformations in the same pot yielding the axially oriented substituent at C-4 and C-5 as the major product in the quinolizidin-2-one and indolizidin-7-one systems, respectively. The thermodynamically more stable isomers 12b and 17 were obtained after basic treatment.