Synthesis of chiral disulfides: potential reagents for enantioselective sulfurization
摘要:
Synthesis of chiral phosphorothioates for use as antisense oligonucleotides might benefit from the use of chiral disulfides. This paper reports the synthesis of chiral analogs of phenylacetyl disulfide and of 5-methyl-3H-1,2,4-dithiazol-3-one from the same set of 2-arylalkanoic acids. The X-ray crystal structures of the disulfides derived from (R) and [S]-2-phenylpropanoic acid establish the stereochemistry and the helicity of these materials, and density functional theory calculations suggest that the high specific rotations can be due to preferred retention of this helicity in solution. Chiral HPLC showed that the final products were formed with enantiomeric purities from 86.1% to99.9%. [image omitted].
Sulfurization of Dinucleoside Phosphite Triesters with Chiral Disulfides
摘要:
Sixteen chiral analogues of phenylacetyl disulfide (PADS) and 5-methyl-3H-1,2,4-dithiazol-3-one (MEDITH) were used to sulfurize five dithymidine phosphite triesters, each incorporating a beta-cyanoethoxy or siloxy group. Each mixture of S-p:R-p, phosphite triester diastereomers was combined with approximately one fourth of an equivalent of each of the sulfurizing reagents, and the R-ps:S-ps diastereomer ratios of the resulting phosphite sulfides or phosphorothioates were determined by reverse-phase HPLC. Diastereoselectivities and corresponding diastereomeric excess (de) values were calculated by correcting for the starting triester diastereomer ratios. The highest de values for R-ps and S-ps phosphorothioates were 14.7% and 7.9%, respectively, both using MEDITH analogues.