Abstract: Process for the preparation of substituted pyrazines comprising the reaction of a dihydroxyketone of formula ##STR1## wherein R.sup.1 et R.sup.2 each represent a hydrogen atom, a saturated or unsaturated, linear or branched, hydrocarbon radical having 1 to 6 carbon atoms, or a --CH.sub.2 OH group, with an ammonium salt, or, as the case may be, with an ammonium salt and an acyloin of formula ##STR2## wherein R.sup.3 and R.sup.4 have the meaning indicated in formula (IV). The process is particularly useful for preparing asymmetrical alkylpyrazines.

Abstract: We describe a bioorganic process for the preparation of cyclopentanone and cyclopentenone derivatives of formula ##STR1## by .beta.-oxidation of appropriate substrates, carried out by means of microorganisms.The process is useful for preparation of 3-oxo-2-pentyl-1-cyclopentaneacetic and (Z)-3-oxo-2-(2-pentenyl)-1-cyclopentane-acetic acids and their methyl esters, compounds useful in the perfume and flavor industries.