The reactions of 5- S-cysteinyldopa ( 1), l-α-methyldopa ( 2) and dl- m-tyrosine ( 3) with d-glucose were investigated at 90 °C in phosphate buffer at pH ranging from 5.0 to 9.0. Whereas 1 gave mainly the double Maillard condensation product N, N′-bis(1″-deoxy- d-fructos-1″-yl)-5- S-cysteinyldopa, as an inseparable mixture of β- d-fructopyranosyl and α,β- d-fructofuranosyl derivatives, 2 and 3 gave both Maillard and Pictet–Spengler products, although to different extents and with different regio- and stereochemistry. A peculiar pattern of reactivity was displayed by 2 which gave, besides the Maillard product and the expected 6,7-dihydroxy-1,2,3,4-tetrahydroisoquinoline C-1 diastereoisomeric pairs, the unprecedented 7,8-dihydroxy-1,2,3,4-tetrahydroisoquinoline derivative via the ortho cyclization pathway. Pictet–Spengler cyclization of 2 and 3 proceeded with Felkin–Anh-type asymmetric induction, favouring the 1 R isomer throughout the pH range 5.0–9.0. These results, which highlight the first example of carbohydrate-derived 7,8-dihydroxytetrahydroisoquinoline, provide new insights into the factors governing competition between Maillard and Pictet–Spengler condensation pathways.