Methyl esters, hydroxymethyl-substituted

The hydroxymethyl-substituted methyl esters can then be transesterified with any number of different initiator types to tailor the structure of the polyol to the end-use application, and all from a single raw material source. The stoichiometry of the polyol is adjustable, to produce polyols of any molecular weight. This synthetic strategy was developed by The Dow Chemical Company as the Renuva polyols. 

The starting substrate, protected ot-vinylproline 187 was activated by HATU and coupled with glycine methyl ester hydrochloride to give protected peptide derivatives 188. Further, ozonolysis of these derivatives and subsequent reduction with excess of Na[BH(OAc)3] provided the hydroxymethyl-substituted derivative 189 in... 

AT-[(Acyloxy)methyl] derivatives of active amines and amides have the general formula RK N-CHR O-COR " where R" = H or Me (or an even larger substituent) and COR" is the acyl group. Activation of these derivatives occurs in two steps as depicted in Fig. 8.20, by analogy with the biotransformation of 0-[(acyloxy)methyl] derivatives of phenols (Sect. 8.5.6) [62], The first step is enzymatic or nonenzymatic cleavage of the ester bridge (Fig. 8.20,a), followed by chemical breakdown of the A-(hydroxymethyl) intermediate (see also Chapt. 5 in [81]). Here, again, liberation of toxic formaldehyde, i. e., where R" = H, should be avoided whenever possible by substitution of, e.g., Me at R"... 

Another situation in which the chemically robust nature of the 4-methyI-l, 2,4-triazole-3,5-dione adducts has been exploited is in the synthesis of bicyclobutane derivatives.Addition of 4-methyl-l,2,4-triazole-3,5-dione to bicyclo[1.1.0]butane gave the urazole 20, which was converted to 2,3-diazabicyclo[2.1.1]hex-2-ene and by thermolysis or photolysis back to bi-cyclo[1.1.0]butane. While this is not in itself a useful synthetic sequence, the urazole intermediates in such a sequence can be chemically modified in ways that would be impossible for the bicyclobutanes themselves. Hence for the adduct 21 of dimethyl bicyclo[1.1.0]butane-l,3-dicarboxylate, the ester groups can be modified into ethyl, vinyl, substituted vinyl, hydroxymethyl, bromo and other substituents and this was used to prepare, for example, 1,3-divinylbicyclo[1.1.0]butane (22) and l-ethyl-3-vinylbicyclo[1.1.0]butane. ... 

Although the CSDP acid method was easily applicable to o-methoxy-substituted alcohol 22 (entry 11), o-methyl-substituted alcohol 23 could not be enantioresolved as the CSDP acid esters because of the small difference between o-methyl and hydrogen groups. So, the indirect method was adopted as follows. o-Hydroxymethyl-diphenylmethanol 24 was enantioresolved as CSDP esters, where the primary alcohol moiety was esterified, and the AC of the second-eluted ester was determined by X-ray crystallography (entry 12). Enantiopure alcohol (7 )-(+)-24 was then converted into the target compound (R)-(—)-23. It should be noted that the AC of alcohol 23 was originally proposed on the basis of an asymmetric reaction mechanism, but it was revised later by this study. The data of alcohols 25 and 26 indicate that the HPLC separation as CSDP esters is easier for silyl ethers (entries 13 and 14). ... 

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