5168-91-2

A simple chain-extending approach was established for the scale-up of the monoprotected monodisperse PEG diol materials. Reactions of THP-(OCH2CH2)n—OMs (n=4, 8, 12) with a large excess of commercially available H—(OCH2CH2)n—OH (n=1-4) under basic conditions led to THP-(OCH2CH2)n—OH (n=5-15). Similarly, Me-(OCH2CH2)n—OH (n=4-11, 13) were prepared from Me-(OCH2CH2)n—OMs (n=3, 7, 11). For the chain elongation steps, 40-80% yields were achieved through extraction purification. PEG oligomer libraries I and II were generated in 50-95% overall yields by alkylation or acylation of THP-(OCH2CH2)n—OH (n=1-15) followed by deprotection. Alkylation of Me-(OCH2CH2)n—OH (n=1-11, 13) with X—(CH2)m—CO2R (X=Br or OMs) and subsequent hydrolysis led to PEG oligomer library III in 30-60% overall yields. Combinatorial purification techniques were adapted to the larger-scale library synthesis. A total of 498 compounds, each with a weight of 2-5 g and a minimum purity of 90%, were synthesized.

The mutarotation of glucose, 2,3,4,6-tetra-O-methylglucose, 3-O-hexyl-, 3-O-dodecyl-, 4,6-O-butylidene, 4,6-O-hexylidene, and 4,6-O-decylidene-glucose has been studied kinetically in aqueous solution and in the following surfactant-solvent systems: AOT-heptane, AOT-CHCl3, CPC-CHCl3, CTAC-CHCl3, CPS-CHCl3 and C16E6-tetradecane.Below a low critical surfactant concentration, mutarotation is undetectably slow, but above it the rate increases, usually in a sigmoidal fashion reaching a maximum value at concentrations above ca. 40 mmol l-1.Maximum rates are usually less than those observed in water except for AOT-containing systems which often, but not always, give higher rates.The dependence of rate on surfactant concentration does not in general fit the pseudophase model of micellar catalysis, but can be treated using Piszkiewicz's co-operativity model.This indicates in a number of cases bimodal catalytic behaviour, a non-co-operative mode at concentrations just above the critical level, and a co-operative mode giving more efficient catalysis at higher concentrations.For AOT-heptane the bimodal pattern is reversed and evidence is presented that the co-operative effects observed at low surfactant concentrations propbably represent catalysis in premicellar aggregates.N.m.r. spectroscopic stiudies (δ, T1) of the protons of water solubilised in the surfactant-solvent systems are reported but do not show helpful correlations with catalytic efficiency in the system studied.A better guide to catalytic efficiency is provided by solvatochromic measurements using N-hexadecylpyridinium iodides incorporated into the catalytic aggregates to report on the polarity in the interior.A possible extension to this approach is discussed.