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Two routes leading to the optically active title compound (9) are described. The first uses, as intermediates, lactonic acids, prepared from enantiomers of 1 -methylcyclohex-4-ene-l,2-dicarboxylic acids ; the absolute configurations of these enantiomers are thereby established. The second, preferred, route starts from 5-methoxy-Z-methylbenzoic acid and, proceeding via the intermediates (21), (5). and (8) affords the diol (9) in 14% overall yield. THE title compound (9),'f used for the synthesis2 of tachysterol,, was originally prepared from 2-ethoxybutadiene by way of l-methyl-4-oxocyclohexane-cis-1,Z-dicarboxylic acid, the lactonic acids (15) and (14), and the hydroxy-ester (8); the route was long, and the overall yield (ca. 0.25~0) low. In connection with recent work on the synthesis of precalciferol, considerable amounts of the diol were required, and we were obliged to seek more efficient ways of preparing it.5At first, in line with the earlier work,3 our ideas centred on the use of intermediates such as the lactonic acids (14) and (4), and methods for their preparation were explored. The readily available frauts-dicarboxylic acid rac-(1) 7 was resolved by the use of quinine, giving both the enantiomers in good yield. The (+)enantiomer which, as will become clear, has the absolute configuration (l), was converted via its anhydride into the crystalline monomethyl ester (2). The corresponding bromolactonic ester (3) reacted with triphenyltin hydride giving the methyl ester of the lactonic acid (4).The free lactonic acid was then obtained by hydrolysis with alkali followed by re-lactonisation of the product with acid. Treatment of the acid (4) with lead tetraacetate in hot benzene containing pyridine and copper(I1) acetate gave a crystalline tertiary acetate, probably (7), and an unsaturated lactone fraction which appeared to be mainly (5) mixed with up to 30% of the exocyclic double-bond isomer (6). Pyrolysis of the acetate (7) provided more of the lactone (5). Treatment of the mixture of unsaturated lactones with methanolic sodium methoxide gave the ester (8), which was then reduced to give the diol (9) in ca. 9% overall yield from the racemic dibasic acid rac-(1).When this route was planned, we anticipated the possibility of using, as well as the enantiomer (l), the ' unwanted ' enantiomer e f i f -( l ) for transformation into the required diol (9). The first step of the projected route, the epimerisation of the enantiomer e d -( l ) , via its anhydride, to give the cis-dibasic acid (lo), [a]= -4.8" (in A brief account of part of this work has appeared: T. M. Dawson, J. Dixon, B. Lythgoe, and I. A. Siddiqui, Chem. Comm., 1970, 992.

The rates of nucleophilic reaction of pyridine and pyrazine with propylene and isobutylene oxides have been measured and compared with related data. No nucleophilic activity can be detected for tetramethylpyrazine, and this base forms an effective buffer in the pH range 3-4.A precision of 3 4 % may be attained when rates of epoxide hydrolysis are measured in tetramethylpyrazine-perchlorate buffer solutions at pH 3.5. The rate coefficient for the acid-catalysed hydrolysis of 0.lM-aqueous isobutylene oxide a t 25.7" is within the range 7.35 f 0.24RATES of epoxide hydrolysis have been studied for pH values near 7 in solutions of non-nucleophilic buffers in order to avoid interference from the acid-catalysed reaction induced through pH drift.l 2,6-Dimethylpyridine, which buffers near pH 7, and closely related molecules in which the functional group is sterically shielded, were shown to be anucleophilic toward the nucleophile-sensitive propylene oxide molecule. This was demonstrated by the absence of the general bimolecular reaction of epoxides with tertiary amines (N) : important3 Here we explored the relative nucleophilicities of pyridine, pyrazine, and tetramethylpyrazine towards epoxides with a view to the use of the latter amines in anucleophilic buffers suitable for the acid pH range.The rate for the acid-catalysed hydrolysis of epoxides is proportional to concentration of epoxide and concentration of hydrogen ions over the pH range 0-6 (and to the Hammett acidity function for negative values of P H ) . ~. ~The reaction proceeds by way of a very small Rat e-det ermi ni ng Re Iat ive l y -ra pid step. step.Perchloric acid was used a sthe buffering agent, owing to the extremely low nucleophilic activity of the perin other systems in which the absence of nucleophiles is 1

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Aus dem Cyclohexenaldehyd (I) wird mit Chlormethylentriphenylphosphoran ein cis‐trans‐Gemisch des w‐Chlordiens (II) erhalten, dessen Dehydrochlorierung mit Butyllithium l‐Äthinyl‐2‐methylcyclohex‐1‐en (III) ergibt.