Methyl vemolate

Conacher and Gunstone reported the novel conversion of the diene monoepoxide methyl vemolate (187 equation 78) to the cyclopropyl keto isomer (188). Later Italian work supported this conclusion, and furnished additional examples of cyclopropane formation. 

Fission-rearrangement of epoxides. Following his suggestion that epoxy-acids may be important intermediates in biosynthesis,19 Gunstone with Conacher 20 found that when the unsaturated epoxy ester methyl vemolate (1) is treated with boron trifluoride etherate in cold benzene solution it is converted into a number of products, two of which cannot be separated from each other but, together, account for a yield of 34%. On the basis of chemical properties, infrared, NMR, and mass spectra they are believed to be the cis and trans forms of the ketocyclopropane ester (2). 

A homoallylic carbocation can also be made from methyl vemolate (12,13-epoxyoleate) and again this acts as a precursor of cyclopropane eompounds. As already indicated, methyl epoxystearate and BF3 etherate interaet to give 9- and 10-oxostearates. When this reaetion was applied to methyl vemolate in boiling dioxan, the expeeted 0x0 esters were aeeompanied by an oxo-eyelopropane ester, whieh was shown to have flie sfrueture indieated in Seheme 3. The yield of cyclopropane was inereased when the reaction was conducted in benzene solution (Table 2). The keto esters were mixtures of cis and irons isomers (4). The virtual absence of 12-oxo-oleate from the reaction conducted in benzene was confirmed by Ward and van Dorp (7) who reeommended the reaction as a source of 13-oxo-oleate and its reduetion produet 13 -hydroxy oleate. Mueh of this work was also confirmed by an Italian group (8). 

For the synthesis of methyl 9,10 12,13-diepoxystearate (27,30), Euphorbia la-gascae, which is rich in vemolic acid, was used as the raw material. Following a one-step transesterification with MeOH/NaOH, pure methyl vemolate was obtained in high chemical yields by vacuum distillation. Methyl 9,10 12,13-diepoxystearate... 

Figure 1. The percentage of -methyl vemoleate detected from microsome assays conducted with V. galamensis. The percentage reports the amount of product ([ " C]-methyl vemoleate) relative to the total amount of radioactivity detected per lane on TLC. Each percentage is the mean of three assays SE.

The idea of NUS has found considerable interest and applications in the context of the conventional 2D-FT schemes. NUS is also compatible with the covariance spectroscopy. Lafon et al. reported on natural abundance deuterium NMR spectroscopy of 2-ethyloxirane (C4H8O) and methyl vemoleate (C19H34O3) dissolved in chiral polypeptide liquid crystals... 

Remotely unsaturated epoxy acids undergo fission rearrangement when treated with BF3-OEt2. Hence, cis and trans ketocy-clopropane esters are produced from the unsaturated epoxy ester methyl vemolate (eq 27). ... 

Further studies on this topic required the preparation of the four geometrically isomers of methyl 12,15-octadecadienoates-9,10-J2- [50, 51] They were prepared by Wittig reaction between cis- or trans-3-hexenyl-triphenylphosphonium bromide and methyl 12-oxododecanoate-9,10-c/2 prepared from vemolic acid as above described. 

---