6-fluoro-3,5-dihydroxy carboxylic acids and derivatives thereof

(3R,5S,6E)-6-Fluoro-3,5-dihydroxy-hept-6-enoic acids and the derivatives thereof of formula I ##STR150## and the corresponding (4R,6S)-6-(1-fluoro-vinyl)-4-hydroxytetrahydro-pyran-2-ones of formula II ##STR151## where, in formulas I and II, R.sup.1 denotes the group of substituted 6-membered ring heteroaromatics ##STR152## in which Z denotes a nitrogen atom, and

• R.sup.3, R.sup.4 and R.sup.5 independently denote hydrogen, a straight chain or branched alkyl or alkenyl radical, each of which has up to 6 carbon atoms and which can optionally be substituted on the terminal carbon by a cycloalkyl or cycloalkenyl radical, each of which has 3-6 carbon atoms, or denote a cyclic hydrocarbon radical which is saturated or up to doubly saturated and has 3-7 carbon atoms, or an aromatic radical selected from the group consisting of phenyl, furyl, thienyl and pyridinyl, which can optionally carry in the nucleus 1-3 identical or different substituents from the following group:
• halogen, trifluoromethyl, alkyl or alkenyl, each of which has up to 6 carbon atoms, hydroxyl, alkoxy having 1-6 carbon atoms, carboxyl or carbalkoxy having 1-6 carbon atoms in the alkoxy moiety.