C5-P bond analogs

Figure 1 shows a 50 MHz CP/MAS C NMR spectrum of ramie cellulose and a stick-type nmr spectrum of low molecular weight cellulose( DP <10) In deuterated dimethyl sulfoxide solution(DMSO) (8 ) (The broken and solid lines In the CP/MAS spectrum will be explained below.). As already reported(9,10), the assignments for the Cl, C4 and C6 carbons are relatively easy, based on analogies with the solution state spectrum. However, It should be noted that these resonance lines shift downfleld by 2.3-9.6 ppm In the solid state compared to the solution state. The cause of such large downfleld shlfts(to be explained In the next section) Is attributed to the different conformations about the P-l,4-glycosldlc linkage and the exo-cyclic C5-C6 bond in which these carbons are Involved. 

Isomerization of inter-nucleosidic 3 -0-P-CH2-5 and 3 -O P H(OH)-5 phos-phonate linkages to their 2, 5 -counterparts has been studied over a wide pH-range. The model compounds employed are phosphonate analogs of adenylyl-(3, 5 )-adenosine and adenylyl-(2, 5 )-adenosine having either adenosine R,5-(50) or R,5-(51) or 5 -deoxyadenosine (52, 53) bonded to the phosphorus atom through the C5 -atom. 

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