Patent ID: 7211668

Claim:
A compound having formula I: wherein E is sulfur or oxygen; J is nitrogen or C—R′; R1, R′ is independently H, halogen, alkyl, nitro, alkoxy, halogenated alkyl, halogenated alkoxy or a functional group having one of following general formulae: wherein A 1 , A 2 , A 3 , A 4 , A 5 , is independently selected from H, halogen, CF 3 , alkyl, nitro, cyano, alkoxy, halogenated alkyl, halogenated alkoxy, phenyl, and halogenated phenyl; R2 is H or protected or unprotected side chain of natural α-amino acid; and B is a natural nucleobase, wherein when said nucleobase has an exocyclic amino function, said function is protected by protecting group which is labile to acids but stable to organic bases in the presence of thiol, wherein the organic bases are triethylamine, N,N-diisopropyethylamine, piperidine, N-methylmorpholine, or 1,8-diazabicyclo[5,4,0]undec-7-one; and the thiol is C2˜C20 alkanethiol, 4-methoxytoluenethiol, 4-methylbenzenethiol, 3,6-dioxa-1,8-octanethiol,4-chlorotoluenethiol, benzylmercaptane, N-acetylcysteine, N-(t-Boc)cysteine methyl ester, methyl 3-mercaptopropionate, or 4-methoxybenzenethiol.