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the natural effector of Hb, does inside the red blood cell. For these reasons we have investigated the phosphorylation of dextran by tetrapolyphosphoric acid [1]. The characterization of dextran phosphates thus obtained, which was carried out by 31P-NMR, high performance gel filtration and the potentiometric method, did not confirm the previously published assumption [1] concerning the structure of the phosphate moieties. We have shown that in fact this phosphorylation method mainly led to two kinds of phosphate ester: monoalkylmonophosphate and monoal- kyldiphosphate. By using a mild acidic treatment, it was then possible to transform the monoalkyldiphosphate species into monoalkylmonophosphate ones. These dextran monoalkylphosphates were found to provoke a decrease in the affinity of Hb for oxygen, which means that they specifically interact inside the protein allosteric site. Therefore, in a second step, we investigated the covalent coupling of dextran phosphates onto deoxyhemoglobin, and determined those which preserved this effect of decreasing oxygen affinity. The new oxygen carriers thus obtained could be of interest in the field of intravascular use as they exhibit a low oxygen affinity and a high molecular weight.

1 Arch. Biochem. Biophys., 135 (1969) 396.

To be published as "A Re-investigation of Phosphorylation of Dextran with Polyphosphoric Acid: Evidence for the Formation of Different Types of Phosphate Moieties" in Carbohydrate Research.

Solid-phase Phosphatidylethanolamine Synthesis M. Tomoi, Y. Kimura and H. Kakiuchi, Yokohama National University, Japan

It is necessary to protect the amino group of glycerophosphorylethanolamine (I) in the synthesis of phosphatidyl- ethanolamine (II) by the acylation of I. In this study a polymer-supported triphenylmethyl group was used as a protective group for the amine. The reaction of L-a-cephalin from egg yolk with polymer-supported triphenylmethyl chloride, crosslinked with 1 or 2 mole% of DVB, afforded immobilized II in which the amino group was protected by the supported triphenylmethyl. The treatment of the immobilized II with CHaONa in a C H a O H / T H F mixture yielded immobilized I, which was converted into immobilized dipalmitoylphosphatidylethanolamine by the reaction with palmitic anhydride in the presence of DMAP in CHCI 3. The resulting immobilized dipalmitoylphosphatidyl- ethanolamine was treated with CF3COOH in CH2CI ~ to give free dipalmitoylphosphatidylethanolamine in a good yield. Such a solid-phase synthesis resulted in easy separation and purification of lipid intermediate I.

To be published in Synthetic Communications.

Synthesic Applications of the Bromomethyi-Nbb Resin. Esters of a Model for the Natural Pyrrole Pigments by Transesterification of their ortho-Nitrobenzyl Ester Polystyrene Supported Pre- cursors Sbnia Serra and Francesc R. Trull, University of Barcelona, Spain

Bromomethyl-Nbb resin, i.e., a-[(4-bromomethyl-3-nitrobenzamido)benzyl]-poly(styrene-co-divinylbenzene), has been used to efficiently link through one (or, more often two) ortho-nitrobenzyl ester bond(s) both linear and cyclic pyrrole pigments containing one (or two) carboxylic acid group(s). This gives an activated form of the initial carboxylic acid and, as such, can be exploited for synthetic purposes: treatment at room temperature with a 30 : 9 : 1 d ioxane :MeOH:aq . 4 N NaOH solution (3 × 3 min) gives the methyl ester derivative almost quantitatively. In the work described here, detachment of a bound dipyrrole with other alcohols under similar conditions has been achieved. With primary, short-chain, linear or non-linear alcohols, the ester yields a re high (99% EtOH, 95% n-PrOH, 60% n-BuOH, 70% i-BuOH, 76% neo-PentOH), but decrease rapidly with chain length (40% n-DecOH, ca. 0% n-CetOH). With secondary and tertiary alcohols, no ester is obtained. The results are interpreted in terms of the lack of amphiphilicity of these alcohols, i.e., the impossibility of obtaining homogeneous 30 :9 :1 d ioxane :MeOH:aq . 4 N NaOH mixtures with them. Unsuccessful attempts to overcome this included using other aqueous bases such as KOH and (n-Bu)4OH , amines such as Et3N, EDIA, pyridine and imidazole, as well as non-aqueous d i o x a n e : R O H : R O - mixtures. An additional, chemical rationalization can be made in terms of a BAc 2 mechanism, involving a tetrahedral

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intermediate, which is therefore more hindered for secondary and tertiary alcohols. Analogous treatment with 1.3 N RR 'NH in dioxane gives the methyl (75%), dimethyl (65%) and a-phenethyl (30%) amides.

To be published in Die Makromolekulare Chemie.

Dynamic HPLC on CSP. A New Analytical Method for Determining Rate Constants and Energy Barriers of Interconverting Enantiomers J. Veciana and M.I. Crespo, C.I.D. (C.S.LC.), Barcelona, Spain

The use of chiral polymers as stationary phases (CSPs) in HPLC is a well-known technique that permits in several cases the recognition and complete separation of stable enantiomers. However, when the enantiomerization energy barrier is low, the interconversion process might be in competition with the separation one, giving distorted and characteristic chromatograms depending on the relative rates of both processes. Since the interconversion rate can be experimentally controlled by changing chromatographic conditions (solvent flow rates or temperatures), HPLC would be suitable for the study of dynamic enantiomerizations.

Here is presented for the first time a method based on the above approach which is called Dynamic HPLC on CSP in resemblance to Dynamic NMR. This method is theoretically founded on stochastic considerations developed previously for GC and permits the determination of interconversion rate constants at several temperatures from the chromatographic profiles by using a numerical procedure. The method has been tested with an analytical column of (+)-poly(triphenylmethylmethacrylate) using tris(2,4,6-trichlorophenyl)methane, which shows two interconvertible and resolvable enantiomers due to atropisomerism. The energy barrier of interconversion (E a =17.7 kcal/mol) calculated from an Arrhenius plot is in excellent agreement with the results obtained with Dynamic NMR, demonstrating the reliability of the method.

Other examples of related compounds, including stable free radicals, are also presented. The distinct energy barriers found are discussed in terms of structural and electronic effect.

Regiospecific Introduction of Iodine into Aromatic Molecules by Crosslinked Poly(styrene-4- vinyl(pyridinium dichloroiodate (I))) Boris Sket, Pavle Zupet and Marko Zupan, University of Ljubljana, Yugoslavia

It has been demonstrated that the introduction of fluorine and bromine into organic molecules is possible with polymer-supported reagents, and many advantages of their use have been pointed out. On the other hand, iodination with polymer-supported reagents has received much less attention, although it is known that iodination with several reagents leads to crude reaction mixtures whose purification represents a major problem. We report the reaction of crosslinked poly(styrene-4-vinylpyridine) (42-44% of pyridine rings, 2% DVB) with a mixture of HCI-IC1 resulting in the crosslinked poly(styrene-4-vinyl(pyridinium dichloroiodate(I))) (I), which reacted with various organic molecules, leading to iodinated products as shown below.

Substrate Position of Yield a Reaction functionalization (%) conditions b

N, N-Dimethylaniline 4 80 Phenol 4 60 Anisole 4 85 1-Methoxynaphthalene 4 85 2-Methoxynaphthalene 1 77 1-Naphthol 4 68 2-Naphthol 1 73 1,3,5 -Trimethylbenzene 2 76

A, 25 ° C, 240 rain B, 50 o C, 270 rain A, 65 o C, 120 n'fin B, 50 o C, 300 min A, 50 o C, 210 nun B, 50 ° C, 270 nun A, 65 o C, 120 nun B, 50 ° C, 270 rain

a Yield of product after purification, b 1 mmol of substrate, 0.5 g of I; 20 ml of solvent; A: CH3OH, B: CH3COOH; reaction conditions leading to complete conversion of starting compound as evident from NMR