Biologically Relevant Phosphoranes:  Synthesis and Structural Characterization of Glucofuranose-Derived Phosphoranes with Penta- and Hexacoordination at Phosphorus

Abstract

Carbohydrate-based phosphoranes were synthesized by reacting the appropriate diphenol with phosphorus trichloride followed by the addition of chloralose to form 1 and by the addition of isopropylidene-D-glucofuranose to form 2 and 3. Phosphorane 4 was obtained by reacting 1,2-O-isopropylidene-alpha-D-glucofuranosyl-3,5,6-phosphite (13) with a diphenol. For the synthesis of 5-9, the appropriate phosphite was reacted with isopropylidene-glucofuranose. X-ray analyses of 1-9 were carried out successfully. Hexacoordinated structures resulted via oxygen donor action at phosphorus in the cases of phosphoranes 1-3 and via sulfur donor action for phosphoranes 4-6. Trigonal bipyramidal structures formed for 7-9 with the carbohydrate components occupying axial-equatorial sites. The eight-membered ring of the diphenol moiety with weak or no donor groups in 7-9 occupied diequatorial sites of the trigonal bipyramid. Solution NMR data are in agreement with the assigned solid-state structures. Isomerism between penta- and hexacoordination is present in solution for 7. The isomerism observed for 7 and our previous study showing a rapid exchange process that reorients the carbohydrate component of the trigonal bipyramidal phosphorane suggest that these biophosphoranes may serve as models for active sites of phosphoryl-transfer enzymes. At an active site, this type of pseudorotational behavior provides a mechanism that could bring another active site residue into play and account for a means by which some phosphoryl-transfer enzymes express promiscuous behavior.

Crystal structure of 4-methyl-2,6,7-trioxa-1-phosphabicyclo[2.2.2]octane

“…In particular, we have noted interesting studies comparing the donor ability of bicyclic phosphites and the related acyclic phosphites; the phosphorus atom in the former shows more positive charge than in the acyclic phosphites and, hence, the donor ability of bicyclic phosphites is lower than that of the related acyclic phosphites (Vande Griend et al, 1977;Joslin et al, 2012). The present work is a continuation of an investigation into the synthesis and study of bi-and tri-cyclic, penta-and hexa-coordinated phosphoranes to form anionic, neutral and zwitterionic compounds (Said et al 1996;Timosheva, et al 2006;Kumara Swamy & Satish Kumar, 2006). In this paper, we report the synthesis, clean isolation and crystal structure of 4-methyl-2,6,7-trioxa-1phosphabicyclo[2.2.2]octane (Tolman, 1977;Joslin et al, 2012).…”

Hydrido-bis(meso-oxolanylen-3,4-dioxy)-λ5-phosphane

“…17−25 A puckering analysis of the five-membered rings according to Cremer and Pople shows the chelate ring, as well as FIGURE 1 Molecular structure of P(AnErytH −2 )Cl(1) (50% probability ellipsoids). Selected distances (inÅ) and angles (in • ): Cl-P 2.1152(7), P-O13 1.6008(13), P-O12 1.6041(13), O12-C12 1.4459(18), O13-C13 1.4511 (19), C12-C13 1.542(2), O13-P-O12 95.48(6), O13-P-Cl 100.10(5), O12-P-Cl 99.90(5), C12-O12-P 112.82(9), C13-O13-P 112.99(9), O12-C12-C13-O13 −0.22 (16); ring puckering analysis 9 : P-O12-C12-C13-O13 Q 2 = 0.2325(12)Å, ϕ 2 = 0.4(4)…”

Recent knowledge and innovations related to hexofuranosides: structure, synthesis and applications

“…Holmes group is among the major actors of this domain and his team has recently prepared and solved the X-ray structures of several biologically relevant phosphoranes based on glucofuranose and xylofuranose. [229][230][231] One example is represented in Figure 30.…”