Novel compounds of the general formula (XIX) ##STR1## where R.sup.9 is selected from lower alkyl, phenyl, phenyl substituted by one or more hydroxy or lower alkoxy, or pyridyl, are disclosed.A method of making the compounds of Formula (XIX) is disclosed, which comprises heating in aqueous acid a compound of formula (XX) ##STR2## wherein R.sup.10 is selected from lower alkyl, phenyl, phenyl substituted by one or more hyroxy or lower alkoxy or pyridyl and R.sup.11 is selected from lower alkyl, phenyl, substituted by one or more hydroxy or lower alkoxy, pyridyl or --CO.sub.2 R where R is lower alkyl.