DETAILED DESCRIPTION We claim: 1. A compound of formula ##STR5## wherein R. sup. 1 is a member selected from the group consisting of hydrogen, hydroxy, thiohydroxy, lower alkyl, phenyl, naphthyl and pyridyl; R. sup. 2 is a member selected from the group consisting of hydrogen and lower alkyl; E is a member selected from the group consisting of hydrogen, hydroxy, thiohydroxy, lower alkyl and S[CH. sub. 2 CH(R. sup. 1)CH. sub. 2 A]. sub. b (CH. sub. 2). sub. a SiXYZ; A is a member selected from the group consisting of O, OCH. sub. 2, S and SCH. sub. 2 ; B and D are members selected from the group consisting of O, OCH. sub. 2, S or SCH. sub. 2, with the proviso that if B is O or OCH. sub. 2 then D must be S or SCH. sub. 2 and if D is O or OCH. sub. 2 then B must be S or SCH. sub. 2 ; X is a member selected from the group consisting of chlorine, methoxy, ethoxy; Y and Z are members selected from the group consisting of chlorine, methoxy, ethoxy, methyl, ethyl and halogenated substituents thereof; and a is an integer from 2 to about 10; b is an integer of 0 or 1; c is an integer of 1 to about 5; d is an integer of 0 to about 5. 2. A compound as defined in claim 1 wherein a is 3, b is 1, c is 1, d is 0, R. sup. 1 is hydroxy, R. sup. 2 is hydrogen, A is oxygen, B is sulfur, E is SCH. sub. 2 CH(OH)CH. sub. 2 O(CH. sub. 2). sub. 3 SiXYZ, and X, Y and Z are methoxy. 3. A compound as defined in claim 1 wherein a is 3, b is 1, c is 1, d is 1, R. sup. 1 is hydroxy, R. sup. 2 is hydrogen, A is oxygen, B and D are sulfur, E is SCH. sub. 2 CH(OH)CH. sub. 2 O(CH. sub. 2). sub. 3 SiXYZ, and X, Y and Z are methoxy. 4. A compound as defined in claim 1 wherein E is S[CH. sub. 2 CH(R. sup. 1)CH. sub. 2 O]. sub. b (CH. sub. 2). sub. a SiXYZ. 5. A compound of formula ##STR6## wherein R. sup. 1 is a member selected from the group consisting of hydrogen, hydroxy, thiohydroxy, lower alkyl, phenyl, naphthyl and pyridyl; R. sup. 2 is a member selected from the group consisting of hydrogen and lower alkyl; E is a member selected from the group consisting of hydrogen, hydroxy, mercapto, lower alkyl and S[CH
|