Premium
Synchronous bond molecular dynamics of conjugated chlorocyclopropyl alk‐yn‐enes revealed by ECD and UV–vis
Author(s) -
Skepper Colin K.,
Molinski Tadeusz F.
Publication year - 2020
Publication title -
chirality
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.43
H-Index - 77
eISSN - 1520-636X
pISSN - 0899-0042
DOI - 10.1002/chir.23240
Subject(s) - chemistry , substituent , conjugated system , alkene , hyperconjugation , double bond , stereochemistry , circular dichroism , photochemistry , computational chemistry , organic chemistry , molecule , polymer , catalysis
Chlorocyclopropanes (CCPs) conjugated to alk‐yn‐enes occur in a unique family of polyketide natural products from marine sponges. Synthesis of several optically enriched analogs of CCPs and measurement of their UV–vis spectra and electronic circular dichroism (ECD) spectra reveal unusually strong hyperconjugation that constrains and aligns the cyclopropyl C‐C bond with the π‐plane of the distal ene‐bond. This alignment imposes a barrier to rotation of at least 5.0 kcal·mol −1 . Comparison of red‐shifted Cotton effects in chiral CCPs show the barrier is independent of alkene substituent and establishes an empirical rule for assignment of other CCP‐containing natural products.