Performic acid anti hydroxylation

Extensive structure modulations were performed to obtain more potent and less toxic anti-cancer agents, such as etoposide used in the therapy of numerous cancers (Fig. 41) [113], In contrast to podophyllotoxin, etoposide derivatives act as DNA topoisomerase II inhibitors. Tafluposide (F 11782) is an etoposide where both hydroxyl functions of the glycoside moiety are acylated with the pen-tafluorophenoxyacetic acid (Fig. 41). It has been demonstrated that tafiuposide does not act as a pro-drug of etoposide, but through a specific mechanism of interaction with both topoisomerases I and lla [114]. 

Drugs. Antiepilepsy drugs, particularly phenytoin, primidone and phenobarbital, occasionally cause a macrocytic anaemia that responds to folic acid. This may be due to enzyme induction by the antiepileptics increasing the need for folic acid to perform hydroxylation reactions (see Epilepsy) but other factors such as reduced absorption may be involved. Administration of folic acid causes a recurrence of seizures in some patients. Some anti-malarials, e.g. pyrimethamine, may interfere with conversion of folates to the active tetrahydrofolic acid, causing macrocytic anaemia. Methotrexate, another folate antagonist, may cause a megaloblastic anaemia especially when used long-term for leukaemia, rheumatoid arthritis or psoriasis. 

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