Pyridoxal 5-phosphatc

In the liver, all three forms are converted to pyridoxal 5-phosphatc, which circulates in the blood bound to albumin. 

The vinylic and acetylenic analogues of pyridoxal 5 -phosphatc are known. The former can be prepared as a cis-trans mixture by Peterson reaction between a ,3-O-isopropylideneisopyridoxal and diethyl l-lithio-l-(trimethylsilyl)methylphosphonate. Isolation of the cis derivative and subsequent deprotection of the alcohol followed by oxidation with MnO2 in ("HCl, leads to the diethyl... 

Hunter, J. E., and Harper, A. E. (1976) Stability of some pyridoxal phosphatc-dcpcrLdent enzymes in vitamin B-6 deficient rats. ), iVnJr, 106, 653-664. 

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