Thiophosphoramidites

A compound of formula (II)

• wherein
• X is oxygen, sulfur, —CRaRb—, —C(Ra)═C(Rb)—, —C(═CRaRb)—, —C(Ra)═N—, —Si(Ra)2—, —SO2—, —NRa—;
• —O—NRa—, —NRa—O—, —C(=J)-, Se, —O—NRa—, —NRa—CRaRb—, —N(Ra)—O— or —O—CRaRb—;
• Y is oxygen, sulfur, —(CRaRb)n—, —CRaRb—O—CRaRb—, —C(Ra)═C(Rb)—, —C(Ra)═N—, —Si(Ra)2—, —SO2—, —NRa—, —C(=J)-, Se, —O—NRa—, —NRa—CRaRb—, —N(Ra)—O— or —O—CRaRb—;
• with the proviso that —X—Y— is not —O—O—, Si(Ra)2—Si(Ra)2—, —SO2—SO2—, —C(Ra)═C(Rb)—C(Ra)═C(Rb), —C(Ra)═N—C(Ra)═N—, —C(Ra)═N—C(Ra)═C(Rb), —C(Ra)═C(Rb)—C(Ra)═N— or —Se—Se—;
• J is oxygen, sulfur, ═CH2 or ═N(Ra);
• Ra and Rb are independently selected from hydrogen, halogen, hydroxyl, cyano, thiohydroxyl, alkyl, substituted alkyl, alkenyl, substituted alkenyl, alkynyl, substituted alkynyl, alkoxy, substituted alkoxy, alkoxyalkyl, alkenyloxy, carboxyl, alkoxycarbonyl, alkylcarbonyl, formyl, aryl, heterocyclyl, amino, alkylamino, carbamoyl, alkylaminocarbonyl, aminoalkylaminocarbonyl, alkylaminoalkylaminocarbonyl, alkylcarbonylamino, carbamido, alkanoyloxy, sulfonyl, alkylsulfonyloxy, nitro, azido, thiohydroxylsulfidealkylsulfanyl, aryloxycarbonyl, aryloxy, arylcarbonyl, heteroaryl, heteroaryloxycarbonyl, heteroaryloxy, heteroarylcarbonyl, —OC(═Xa)Rc, —OC(═Xa)NRcRd and —NReC(═Xa)NRcRd;
• or two geminal Ra and Rb together form optionally substituted methylene;
• or two geminal Ra and Rb, together with the carbon atom to which they are attached, form cycloalkyl or halocycloalkyl, with only one carbon atom of —X—Y—;
• wherein substituted alkyl, substituted alkenyl, substituted alkynyl, substituted alkoxy and substituted methylene are alkyl, alkenyl, alkynyl and methylene substituted with 1 to 3 substituents independently selected from halogen, hydroxyl, alkyl, alkenyl, alkynyl, alkoxy, alkoxyalkyl, alkenyloxy, carboxyl, alkoxycarbonyl, alkylcarbonyl, formyl, heterocylyl, aryl and heteroaryl;
• Xa is oxygen, sulfur or —NRc;
• Rc, Rd and Re are independently selected from hydrogen and alkyl;
• and
• n is 1, 2 or 3;
• R5 is a hydroxyl protecting group;
• Rx is phenyl, nitrophenyl, phenylalkyl, halophenylalkyl, cyanoalkyl, phenylcarbonylsulfanylalkyl, halophenylcarbonylsulfanylalkyl alkylcarbonylsulfanylalkyl or alkylcarbonylcarbonylsulfanylalkyl;
• Ry is dialkylamino or pyrrolidinyl;
• and
• Nu is a nucleobase or a protected nucleobase.