Nucleoside derivatives for library preparation

A Nucleoside derivative having the general formula:

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• Wherein y is a group
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• wherein
• X is a hetero atom selected from the group O, S, Se or a group NR4, wherein R4 is hydrogen or an optionally substituted linear or branched C1-6 alkyl or C2-6 alkenyl:
• R2 is selected from the group consisting of C1-6 alkylen, C2-6 alkylenylen, C2-6 alkynylen, C3-6 cycloalkylen, heterocycloalkylen, —CH2—O—, arylen or heteroarylen, wherein each of the groups R2 are substituted with 0-3 R8 groups independently selected from ═O, ═S, —F, —Cl, —Br, —I, —OCH3, —NO2 or C1-6 alkyl, and
• Ns is a nucleoside analogue consisting of a nucleobase and a backbone unit;
• or Y is —OR3, wherein R3 is H or an acid protective group.
• R(S) is a C1-14 alkylen, C3-10 cycloalkylen, aryl, heterocycloalkyl or heteroaryl substituted by n sidechains S, wherein n is an integer of 0 to 4
• R1 is H, C1-6 alkyl substituted with 0-3 R9 where R9 is independently selected from ═O, Cl, Br, —CN, —OR6, —SR6, —NR6R7, —COOR6, —CONR6R7, —SO2NR6R7 or a Cl-6 alkylen group forming a ringstructure with S
• R6 and R7 are independently selected from H, C1-6 linear alkyl, C1-6 branched alkyl, C1-6 cycloalkyl, aryl, heteroaryl, aralkyl, or hetero aralkyl.
• S is C, 6 linear alkyl, C3-6 branched alkyl, C3-6 cycloalkyl, aryl, heteroaryl, aralkyl, hetero aralkyl substituted with 0-3 R5 where R5 is independently selected from ═O, Cl, Br, —CN, —OR6, —SR6, —NR6R7, —COOR6, —CONR6R7, —SO2NR6R7.
• Z is H, an amino protective group or a group
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• with the proviso, that when Y is not
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• Z is
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