What is described are compounds 1
wherein R represents Br, I or R.sup.1--SO.sub.3, where R.sup.1 is an
unsubstituted or substituted C.sub.1-C.sub.5-alkyl group, or an
unsubstituted or substituted phenyl group;
X is O or NR", where R" is a usual protective group for N; and
R' represents hydrogen, a halogen, such as F, Cl, and Br, a substituted or
unsubstituted C.sub.1-C.sub.7-alkyl group, such as methyl and ethyl, a
substituted or unsubstituted C.sub.2-C.sub.7-alkenyl group, or a
substituted or unsubstituted C.sub.2-C.sub.7-alkynyl group.
