Guang-Zhong Tu

Synthesis, Crystal Structure, and Diastereomeric Transfer of Pentacoordinated Phosphoranes Containing Valine or Iso-Leucine Residue

Pentacoordinated phosphoranes containing valine or iso-leucine residue (2-phenyl-2,75-spiro[1,3,2-phenanthrodioxaphosphole-2,2′-1,3,2-oxazaphospholan]-5′-one) were synthesized through sequential two-step reactions, whereby the reaction products of phenyldichlorophosphine with N,O-bis(trimethylsilyl)valine or iso-leucine were followed by the addition of phenanthrenequione, and the crystals of 4a and 4b were obtained from benzene and hexane mixed solution. The x-ray structure of the crystals 4a and 4b revealed that they are distorted TBP, exhibiting RP absolute configuration. The 31P NMR spectra showed that the SP diastereomer could transfer into the other one RP that came out from the solution during crystallization. Correspondingly, when it was dissolved in solvents the RP diastereomer transferred into the other one SP, and the pair of diastereomers changed each other in solution at room temperature through a phosphonium carboxylate zwitterions intermediate. The work was supported by the National Natural Science Foundation of China (No. 29902003), the National Science and Technology Committee of China, the Chinese Education Ministry, and Tsinghua University.

NEW AND EFFICIENT APPROACH TO THE SYNTHESIS OF PENTACOORDINATE SPIROBICYCLIC PHOSPHORANES

Pentacoordinate spirobicyclic 2-phenoxy-1,3-phenylenedioxo-1,3,2-imino(alkyl)acetoxyphosphoranes are synthesized through a new and efficient method whereby phosphorus pentachloride is displaced stepwise by catechol, an N,O-bis(trimethylsilyl)amino acid and phenol (pathway A) or catechol, phenol and an N,O-bis(trimethylsilyl)amino acid (pathway B); this method has advantages of high yields, rapid reaction times and easy operation, which might provide a new route for the synthesis of other pentacoordinate phosphoranes.

Synthesis and resolution of dinucleotide(TpAZT) phosphoramidates

Abstract Dinucleotide (TpAZT) phosphoramidates were synthesized through Atherton-Todd reaction of dinucleoside H-phosphonates and amino acid methyl esters, and their diastereomers (Rp and Sp) were separated by crystallization. It was showed that the cheap methyl esters of natural alanine and phenylalanine could act as new chiral auxiliaries for large-scale synthesis of dinucleotide analogs.

ONE POT SYNTHESIS OF ARYL THIOPHOSPHORAMIDATE DERIVATIVES OF AZT

ABSTRACT Novel aryl thiophosphoramidate derivatives of the anti-HIV nucleoside analogue 3′-azido-3′-deoxythymidine (AZT) have been prepared by the thiophosphorochloridate chemistry. These materials were designed to act as membrane-soluble prodrugs of the bioactive free nucleotides.