There are prepared compounds of the formula <IMAGE> where R and R1 are saturated and preferably linear alkyl groups in which the sum of carbon atoms in the two alkyl groups is 4 to 30, ONE OF R and R1 can also be hydrogen, R2 is hydrogen or if R3 is hydrogen, then R2 is the group <IMAGE> where n is 1 to 10, R3 is hydrogen or, if {HEAD ~ R2} is {TAIL ~ hydrogen}, then R3 is the group 
There are prepared compounds of the formula < IMAGE > where R and R1 are saturated and preferably linear alkyl groups in which the sum of carbon atoms in the two alkyl groups is 4 to 30 , ONE OF R and R1 can also be hydrogen , R2 is hydrogen or if R3 is hydrogen , then R2 is the group < IMAGE > where n is 1 to 10 , R3 is hydrogen or , if { HEAD ~ R2 } is { TAIL ~ hydrogen } , then R3 is the group
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