Versatile and Functionalised Intermediates for the Synthesis of Vitamin D and Novel Vitamin D Derivatives

A compound of formula (I), its diastereoisomers or its enantiomers

• Wherein each R1 and R2 is independently selected from the group consisting of hydrogen, hydroxyl, alkoxy, aryloxy, alkylcarboxy, arylcarboxy and —OSiP1P2P3,
• R3 is hydrogen or a methylene group (═CH2),
• Each of R4 and R5 is independently selected from the group consisting of hydrogen, hydroxyl, alkoxy, aryloxy, alkylcarboxy, arylcarboxy and —OSiP1P2P3, at least one of R4 and R5 hydrogen,
• X is selected from the group consisting of hydrogen, (C1-C6) alkyl, aryl, arylalkyl, heteroalkyl and heterocycle,
• R6 is selected from the group consisting of hydrogen and alkyl,
• W is selected from the group consisting of —CO2Ra, —CONRaRb and —CN,
• A represents a single or double bond,
• each of P1, P2, P3 is independently selected from the group consisting of alkyl, aryl, arylalkyl and heterocycle,
• each of Ra and Rb is independently selected from the group consisting of hydrogen, alkyl, alkenyl, alkynyl, aryl, arylalkyl and heterocycle,
• with the proviso that if A is a single bond then one of the following conditions is true:
• a) R5 is hydrogen, or b) X is different from —CH3, —CH2CH3, —CH2OH, ethenyl and ethynyl.