ChemInform Abstract: REDUCTION-OXIDATION PROPERTIES OF ORGANOTRANSITION METAL COMPLEXES. PART 22. STEREOSPECIFIC OXIDATIVE CYCLOPROPANE RING OPENING AND REDUCTIVE CYCLOBUTANE RING FORMATION IN POLYCYCLIC HYDROCARBON COMPLEXES OF IRON: X-RAY CRYSTAL STRUCT

1985 ◽  
Vol 16 (37) ◽  
Author(s):  
N. G. CONNELLY ◽  
M. J. FREEMAN ◽  
A. G. ORPEN ◽  
J. B. SHERIDAN ◽  
A. N. D. SYMONDS ◽  
...  
Keyword(s):  
Metal Complexes ◽  
Ring Opening ◽  
Cyclopropane Ring ◽  
Ring Formation ◽  
Polycyclic Hydrocarbon ◽  
X Ray ◽  
Oxidation Properties ◽  
Cyclobutane Ring

scholarly journals Synthesis, biophysical properties, and RNase H activity of 6’-difluoro[4.3.0]bicyclo-DNA

2019 ◽  
Vol 15 ◽  
pp. 79-88 ◽  
Author(s):  
Sibylle Frei ◽  
Adam K Katolik ◽  
Christian J Leumann
Keyword(s):  
Building Block ◽  
Ring Opening ◽  
Structural Investigation ◽  
Cyclopropane Ring ◽  
Cd Spectroscopy ◽  
Rnase H ◽  
Biophysical Properties ◽  
X Ray ◽  
X Ray Crystallography ◽  
Cleavage Assay

Here we present the synthesis, the biophysical properties, and the RNase H profile of 6’-difluorinated [4.3.0]bicyclo-DNA (6’-diF-bc4,3-DNA). The difluorinated thymidine phosphoramidite building block was synthesized starting from an already known gem-difluorinated tricyclic glycal. This tricyclic siloxydifluorocyclopropane was converted into the [4.3.0]bicyclic nucleoside via cyclopropane ring-opening through the addition of an electrophilic iodine during the nucleosidation step followed by reduction. The gem-difluorinated bicyclic nucleoside was then converted into the corresponding phosphoramidite building block which was incorporated into oligonucleotides. Thermal denaturation experiments of these oligonucleotides hybridized to complementary DNA or RNA disclosed a significant destabilization of both duplex types (ΔT m/mod = −1.6 to −5.5 °C). However, in the DNA/RNA hybrid the amount of destabilization could be reduced by multiple insertions of the modified unit. In addition, CD spectroscopy of the oligonucleotides hybridized to RNA showed a similar structure than the natural DNA/RNA duplex. Furthermore, since the structural investigation on the nucleoside level by X-ray crystallography and ab initio calculations pointed to a furanose conformation in the southern region, a RNase H cleavage assay was conducted. This experiment revealed that the oligonucleotide containing five modified units was able to elicit the RNase H-mediated cleavage of the complementary RNA strand.

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