Compounds of the formula ##STR1## {HEAD ~ the symbols} have {TAIL ~ the meaning} described in the specification 
Compounds of the formula # # STR1 # # { HEAD ~ the symbols } have { TAIL ~ the meaning } described in the specification
OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH