General entry to the 3,5-disubstituted indolizidine class of dendrobatid alkaloids. Total syntheses of both enantiomers of indolizidines 195B, 223AB, 239AB, and 239CD from a common chiral synthon
General entry to the 3,5-disubstituted indolizidine class of dendrobatid alkaloids. Total syntheses of both enantiomers of indolizidines 195B, 223AB, 239AB, and 239CD from a common chiral synthon