Total synthesis of quinolizidine alkaloids (-)-lasubine II

Aim: To study and improve enantioselective total synthesis of quinolizidine alkaloid (-)-lasubine II. Methods: A new approach to total synthesis of (-)-lasubine II was established from readily available starting materials, via the new synthetic sequence including the creation of stereogenic centers through two sequential highly stereoselective Roush allylborations, S_N2 cyclization and ring-closing metathesis reactions for the construction of the lasubine's quinolizidine skeleton. Results and Conclusion: The synthesis of natural product (-)-lasubine II has been accomplished by a new synthetic route in an overall yield of 15.3% and its spectrum data, including ¹H NMR, ¹³C NMR, EI-MS, IR and optical rotation, is in agreement with the literature data.