STEREOCHEMICAL ASSIGNMENT OF CHIRAL PHOSPHOTRIESTER ANALOGS WITH ALU-I SITES

The stereochemistry of the diastereomers of a DNA duplex with the 2,2, 2-trichloro-1,1-dimethyl (TCDME) phosphotriester backbone substitution has been assigned by the use of 2D NMR spectroscopy. The duplex (11)C (12)T(13)A(14)G(15)C(16)T(17)T(18)C(19)C(20)] is a substrate of the re striction endonuclease Alu I, with placement of the TCDME group at the G(5)C(6) cleavage site of one strand. The stereochemical orientation of the TCDME group in relation to the structure of the double helix re gulates the ability of Alu I to hydrolyze the complementary recognitio n site. The phosphotriester group of the isomer 1 duplex blocks cleava ge of the complementary strand, while that of the isomer 2 duplex allo ws cleavage to proceed. Within the phosphotriester recognition site, n o hydrolysis is detected nor is any seen when the single-stranded DNA substrate is utilized.