Spiro cross-links: representatives of a new class of glycoxidation products.
Covalently cross-linked proteins are among the major modifications caused by the advanced Maillard reaction. So far, the chemical nature of these aggregates is largely unknown. Investigations are reported on the isolation of 6-[2-[[(4S)-4-amino-4-carboxybutyl]amino]-6,7-dihydroxy-6,7-dihydroimidazo[4,5-b]azepin-4(5H)-yl]-L-norleucine (10) and N-acetyl-6-[(6R,7R)-2-[[4-(acetylamino)-4-carboxybutyl]amino]-6,7,8a-trihydroxy-6,7,8,8a-tetrahydroimidazo[4,5-b]azepin-4(5H)-yl]-L-norleucine (12) formed by oxidation of the major Maillard cross-link glucosepane 1. Independent synthesis and unequivocal structural characterization are given for 10 and 12. Spiro cross-links, representing a new class of glycoxidation products, were obtained by dehydrogenation of the amino imidazolinimine compounds N6-[2-[[(4S)-4-ammonio-5-oxido-5-oxopentyl]amino]-5-[(2S,3R)-2,3,4-trihydroxybutyl]-3,5-dihydro-4H-imidazol-4-ylidene]-L-lysinate (DOGDIC 2) and N6-[2-[[(4S)-4-ammonio-5-oxido-5-oxopentyl]amino]-5-[(2S)-2,3-dihydroxypropyl]-3,5-dihydro-4H-imidazol-4-ylidene]-L-lysinate (DOPDIC 3). These new oxidation products were synthesized, and their unambiguous structural elucidation proved the formation of the spiro imidazolimine structures N6-[(7R,8S)-2-[[(4S)-4-ammonio-5-oxido-5-oxopentyl]amino]-8-hydroxy-7-(hydroxymethyl)-6-oxa-1,3-diazaspiro[4.4]non-1-en-4-ylidene]-L-lysinate (16), N6-(8R,9S)-2-[(4S)-4-ammonio-5-oxido-5-oxopentyl]amino]-8,9-dihydroxy-6-oxa-1,3-diazaspiro[4.5]dec-1-en-4-ylidene)-L-lysinate (19), and N6-[(8S)-2-[(4-amino-4-carboxybutyl)amino]-8-hydroxy-6-oxa-1,3-diazaspiro[4.4]non-1-en-4-ylidene]-L-lysinate (18), respectively. It was shown that reaction of the imidazolinone 15 led to the formation of spiro imidazolones, structurally analogous to 16 and 19.
Reihl
Oliver
O
Institute of Food Chemistry, University of Hohenheim, Garbenstrasse 28, D-70593 Stuttgart, Germany. oreihl@uni-hohenheim.de
Biemel
Klaus M
KM
Eipper
Wolfgang
W
Lederer
Markus O
MO
Schwack
Wolfgang
W
D001381:Azepines / Q000737:chemistry*; D003432:Cross-Linking Reagents; D005504:Food Analysis; D017127:Glycation End Products, Advanced / Q000737:chemistry; D007093:Imidazoles / Q000737:chemistry; D007097:Imines / Q000737:chemistry*; D008239:Lysine / Q000031:analogs & derivatives* / Q000737:chemistry*; D015416:Maillard Reaction; D010084:Oxidation-Reduction; D013141:Spiro Compounds / Q000737:chemistry*
D001381:Azepines; D003432:Cross-Linking Reagents; D017127:Glycation End Products, Advanced; D007093:Imidazoles; D007097:Imines; C495621:N6-((7R,8S)-2-(((4S)-4-ammonio-5-oxido-5-oxopentyl)amino)-8-hydroxy-7-(hydroxymethyl)-6-oxa-1,3-diazaspiro(4.4)non-1-en-4-ylidene)-L-lysinate; C495622:N6-((8R,9S)-2-(((4S)-4-ammonio-5-oxido-5-oxopentyl)amino)-8,9-dihydroxy-6-oxa-1,3-diazaspiro(4.5)dec-1-en-4-ylidene)-L-lysinate; D013141:Spiro Compounds; C117197:imidazolone; D008239:Lysine