L-alloisoleucine (2S, 3R), a diastereomer of L-isoleucine (2S, 3S), is a normal constituent of human plasma. It was shown, that the plasma L-alloisoleucine above the cutoff value of 5 micromol/L is the most specific and most sensitive diagnostic marker for all forms of maple syrup urine disease (MSUD). The precise mechanism of L-alloisoleucine formation is unclear, but existed suggestions, that R-3-methyl-2-oxopentanoate is an immediate and inevitable byproduct of L-isoleucine transamination and that alloisoleucine is primarily formed via transamination of 3-methyl-2-oxopenanoate in vivo.

Idose is an aldohexose isomeric with galactose. Idose can influence to the stability of phospholipid bilayers and topical application of idose accelerated the skin barrier recovery

L-Gulonic acid, a diastereomer of d-gluconic acid is the one of a metabolite in the urinate cycle, is a substrate of L-Gulonate 3-dehydrogenase (GDH). This enzyme catalyzes the NAD(+)-linked dehydrogenation of L-gulonate into dehydro-L-gulonate. L-Gulonic acid is also a metabolite of the D-glucuronic acid pathway. It was suggested, that the measurement of a spectrum of urinary D-glucuronic acid metabolites might provide a more reliable index for assessment of the induction of hepatic xenobiotic-metabolizing enzyme activities in man than the determination of urinary D-glucaric acid alone.