Formation of novel tetrahydroisoquinoline retinoids by Pictet–Spengler reaction of dopamine and retinaldehyde under conditions of relevance to biological environments

Some constituents of vitamin A react with dopamine, under conditions of relevance for biological environments, to give tetrahydroisoquinoline retinoid derivatives. Three main products, from 13-cis retinaldehyde, were isolated in low yields and characterized. The formation of a Schiff base intermediate has been confirmed by HPLC analysis and the effect on reaction course of metal ions has been valued.