A compound of the following structure:
##STR00001## wherein R.sup.1 is H, an alkyl group, an aryl group, an
alkenyl group, an alkynyl group, or a halogen atom; R.sup.2 is H, an
alkyl group, an aryl group, a benzyl group, a trityl group,
--SiR.sup.aR.sup.bR.sup.c, CH.sub.2OR.sup.d, or COR.sup.e; R.sup.a,
R.sup.b and R.sup.c are independently an alkyl group or an aryl group;
R.sup.d is an alkyl group, an aryl group, an alkoxylalkyl group,
--R.sup.iSiR.sup.aR.sup.bR.sup.c or a benzyl group, wherein R.sup.i is an
alkylene group; R.sup.e is an alkyl group, an allyl group, a benzyl
group, an aryl group, an alkoxy group, or --NR.sup.gR.sup.h, wherein
R.sup.g and R.sup.h are independently H, an alkyl group or an aryl group;
R.sup.3 is (CH.sub.2).sub.n where n is and integer in the range of 0 to
5, --CH.sub.2CH(CH.sub.3)--, --CH.dbd.CH--, --CH.dbd.C(CH.sub.3)--, or
--C.ident.C--; R.sup.4
##STR00002## , wherein y1 and y2 are 1 and y3, y4 and y5 are
independently 0 or 1, R.sup.k1, R.sup.k2, R.sup.k3, R.sup.k4 and R.sup.k5
are independently H, CH.sub.3, or OR.sup.2a, and R.sup.s1, R.sup.s2,
R.sup.s3, and R.sup.s4 are independently H or CH.sub.3, wherein R.sup.2a
is H, an alkyl group, an aryl group, a benzyl group, a trityl group,
--SiR.sup.aR.sup.bR.sup.c, CH.sub.2OR.sup.d, or COR.sup.e; and R.sup.5 is
H or OR.sup.2b, wherein R.sup.2b is H, an alkyl group, an aryl group, an
aryl group, a benzyl group, a trityl group, --SiR.sup.aR.sup.bR.sup.c,
CH.sub.2OR.sup.d, or COR.sup.e.
