Synthesis, Isolation, and NMR‐Spectroscopic Characterization of Fourteen (<i>Z</i>)‐Isomers of Lycopene and of Some Acetylenic Didehydro‐ and Tetradehydrolycopenes

Abstract

Abstract Eight ( Z )‐isomers of lycopene were prepared by stereocontrolled syntheses and fully characterized by 1 H‐NMR, 13 C‐NMR, mass, and UV/VIS spectroscopy: (5 Z )‐, (7 Z )‐, (15 Z )‐, (5 Z ,5′ Z )‐, (7 Z ,7′ Z )‐, (7 Z ,9 Z )‐, (9 Z ,9′ Z )‐, and (7 Z ,9 Z ,7′ Z ,9′ Z )‐lycopene. Six additional ( Z )‐isomers, namely (9 Z )‐, (13 Z )‐, (5 Z ,9′ Z )‐, (9 Z ,13′ Z )‐, (5 Z ,9 Z ,5′ Z )‐, and (5 Z ,13 Z ,5′ Z )‐lycopene, were isolated in small quantities from isomer mixtures by semiprep. HPLC and were identified by 1 H‐NMR spectroscopy.