The absolute configuration of elemol has been proved to be as shown in formula (V) by a synthesis of eleman-2,3,1 l-trio1 (XXXIII) from (+)-epia-cyperone (XI), a sesquiterpene of known absolute configuration.ELEMOL is a crystalline, unsaturated, tertiary-alcoholic sesquiterpene which has structure An indication of its relative stereochemistry is given by the formation of the lactone (111) from dihydroelemol (11), while the isolation of eudesmane (IV) on hydrogenation of the mixed hydrocarbons obtained by pyrolysis of elemyl benzoate or p-nitrobenzoate suggests, but does not prove, that the absolute configuration is as in structure (V). This has now No decisive proof of its absolute configuration has been published. * Part VII, J . , 1961, 4211.
Nitro-L-arginine can be reduced at a mercury cathode to L-arginine nearly quantitatively, and this new method for the removal of the nitro-group has been used in the synthesis of L-arginyl-L-leucine, -L-valine, -glycine, -L-proline, -S-benzyl-L-cysteine, and -S-benzylthiomethyl-L-cysteine, and of L-prolyl-L-arginine. The procedure succeeds with sulphur-containing peptides, for which catalytic hydrogenation fails. By the use of a mixture of tetrahydrofuran and N-sulphuric acid as solvent during the reduction, Na-benzyloxycarbonyl-Nu-nitro-L-arginylglycine was converted into NQ-benzyloxycarbonyl-L-arginylglycine.
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