Fig. 4: Origin of diastereo- and enantioselectivity, reactivity of monocyclic intermediates and mechanistic proposal.
From: The catalytic asymmetric polyene cyclization of homofarnesol to ambrox

a, Identified intermediates and products in the reaction of 1a to 2a in HFIP or PFTB. b, Yield, enantiomeric excess (e.e.) and diastereomeric excess (d.e.; 2a:2c) over time in HFIP/1H,1H-perfluorooctan-1-ol at −23 °C according to gas chromatography and HPLC analysis. c, Reactivity of cyclohomofarnesols 3 in HFIP and PFTB. d, Mechanistic proposal for the formation of 2a and its diastereomer 2c in HFIP/1H,1H-perfluorooctan-1-ol and PFTB.