Preparation of deuterium‐labelled retinals having high deuterium content on specific positions 10‐Mono‐, 11‐mono‐, 10,11‐di‐ and 14,20,20,20‐tetradeuterioretinal

Abstract

Abstract 10‐Mono‐, 11‐mono‐ and 10,11‐dideuterioretinal (in the all‐trans, 9‐cis, 11‐cis and 13‐cis forms) of > 98% purity and the required (> 96%) deuterium incorporation were prepared via LiAlH 4 or LiAlD 4 reduction of the retinylidene derivative 8. Compound 8 was prepared by coupling β‐ionone with 6,6‐dimethoxy‐4‐methyl‐3‐hexen‐1‐yne (6), which had been obtained in high yield from 2‐propynyl bromide and commercial 4,4‐dimethoxy‐2‐butanone (4). Exchange of 4 with D 2 O and base gave 4,4‐dimethoxy‐1,1,1,3,3‐pentadeuterio‐2‐butanone (4a), which in turn, using the same synthetic method, finally provided 14,20,20,20‐tetradeuterioretinal.