The reactions of 5-S-cysteinyidopa (1), L-alpha-methyldopa (2) and DL-m-tyrosine (3) with D-glucose were investigated at 90 degrees 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 beta-D-fructopyranosyl and alpha,beta-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 I 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.

Reactions of D-glucose with phenolic amino acids: further insights into the competition between Maillard and Pictet-Spengler condensation pathways

D'ISCHIA, MARCO
2005

Abstract

The reactions of 5-S-cysteinyidopa (1), L-alpha-methyldopa (2) and DL-m-tyrosine (3) with D-glucose were investigated at 90 degrees 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 beta-D-fructopyranosyl and alpha,beta-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 I 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.
File in questo prodotto:
Non ci sono file associati a questo prodotto.

I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.

Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11384/84363
 Attenzione

Attenzione! I dati visualizzati non sono stati sottoposti a validazione da parte dell'ateneo

Citazioni
  • ???jsp.display-item.citation.pmc??? ND
  • Scopus 15
  • ???jsp.display-item.citation.isi??? 14
  • OpenAlex ND
social impact