Synthesis of 6-s-cis and 6-s-trans A-ring modified vitamin D analogues.

Vitamin D, through its hormonally active form 1α,25-dihydroxyvitamin D3 [1α,25- (OH)2-D3], exhibits a much broader spectrum of bio logical activities than expected in the endocrine system. However, 1α,25-(OH)2-D3 causes hypercalcemia a t pharmacologically r elevant doses wh ich forms a major obstacle in the clinical development of this compound. As a result, considerable effort has been made toward the synthesis of potential chemotherapeutic structurally related congeners with dissociation of beneficial effects from their toxic effects.

Whole-cell biotransformation with recombinant cytochrome P450 for the selective oxidation of Grundmann's ketone.

25-Hydroxy-Grundmann's ketone is a key building block in the chemical synthesis of vitamin D3 and its derivatives through convergent routes. Generally, the chemical synthesis of this compound involves tedious procedures and results in a mixture of several products. Recently, the selective hydroxylation of Grundmann's ketone at position C25 by cytochrome P450 (CYP) 154E1 from Thermobifida fusca YX was described.

Synthesis of vitamin D3 analogues with A-ring modifications to directly measure vitamin D levels in biological samples.

C-3-substituted 25-hydroxyvitamin D3 analogues were synthesized as tools to directly measure levels of vitamin D in biological samples. The strategy involves vinyloxycarbonylation of the 3β-hydroxy group and formation of a carbamate bond with a hydroxyl or amino group at the end of the alkyl chain. Biotinylated conjugates of synthesized derivatives were generated to be linked with vitamin D binding protein (DBP).

Horseradish peroxidase covalent grafting onto screen-printed carbon electrodes for levetiracetam chronoamperometric determination.

A new enzymatic electrochemical biosensor based on disposable transducers, namely screen-printed carbon electrodes, has been developed for the determination of the antiepileptic drug levetiracetam. Horseradish peroxidase was immobilized onto the carbon working electrode previously modified by an aryl diazonium salt. The formation of amide bonds between the amino and carboxylic groups of the enzyme surface, catalyzed by hydroxysuccinimide and carbodiimide, leads to the electrode functionalization.