Fluorescent dyes

A compound represented by Formula I:

• or a stereoisomer, a salt, or a tautomer thereof,
• wherein:
• X is H, halogen, or C1-C05 alkyl;
• R1, R2, R3, and R4 are independently H or optionally substituted C1-C6 alkyl;
• R5, R6, R7, R8, and R9 are independently H, halogen, or optionally substituted C1-C6 alkyl;
• L1 is an optionally substituted C2-C10 alkylene or optionally substituted C2-C50 heteroalkylene;
• L2 and L3 are independently an optionally substituted C2-C10 alkylene or optionally substituted C2-C30 heteroalkylene;
• Q1 is a hydroxyl protecting group;
• Z is CH, N, NHC(O)N, or OC(O)N;
• Y is OH, OP(OCH2CH2CN)NR10R11, or a solid support;
• and
• R10 and R11 are independently optionally substituted C1-C6 alkyl.