Stereoselectivity in N-Iminium Ion Cyclization: Development of an Efficient Synthesis of (±)-Cephalotaxine.
A stereoselective N-iminium ion cyclization with allylsilane to construct vicinal quaternary-tertiary carbon centers was developed for the concise synthesis of (±)-cephalotaxine. The current strategy features a TiCl4-promoted cyclization and ring-closure metathesis to furnish the spiro-ring system. The stereochemical outcome in the N-acyliminium ion cyclization was rationalized by the stereoelectronic effect of the Z- or E-allylsilane. Two diastereomers arising from the cyclization were merged into the formal synthesis of (±)-cephalotaxine.
CAS Key Laboratory of Synthetic Chemistry of Natural Substances and ‡CAS Key Laboratory of Organofluorine Chemistry, Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences , 345 Lingling Road, Shanghai 200032, China.
Hao
H
Liu
CAS Key Laboratory of Synthetic Chemistry of Natural Substances and ‡CAS Key Laboratory of Organofluorine Chemistry, Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences , 345 Lingling Road, Shanghai 200032, China.
Jing
J
Yu
CAS Key Laboratory of Synthetic Chemistry of Natural Substances and ‡CAS Key Laboratory of Organofluorine Chemistry, Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences , 345 Lingling Road, Shanghai 200032, China.
Xinyu
X
Li
CAS Key Laboratory of Synthetic Chemistry of Natural Substances and ‡CAS Key Laboratory of Organofluorine Chemistry, Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences , 345 Lingling Road, Shanghai 200032, China.
Rui
R
Yan
CAS Key Laboratory of Synthetic Chemistry of Natural Substances and ‡CAS Key Laboratory of Organofluorine Chemistry, Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences , 345 Lingling Road, Shanghai 200032, China.
Ji-Chang
JC
Xiao
CAS Key Laboratory of Synthetic Chemistry of Natural Substances and ‡CAS Key Laboratory of Organofluorine Chemistry, Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences , 345 Lingling Road, Shanghai 200032, China.
Ran
R
Hong
D003500:Cyclization; D006248:Harringtonines / Q000138:chemical synthesis* / Q000737:chemistry; D000077863:Homoharringtonine; D007097:Imines / Q000737:chemistry*; D015394:Molecular Structure; D013237:Stereoisomerism
D006248:Harringtonines; D007097:Imines; D000077863:Homoharringtonine