Build a straight, saturated 15-carbon chain numbered left to right C1-C15, with all single bonds. At the left terminus (C1), attach two substituents directly to that carbon:

1. Sulfonic acid group: connect the sulfur atom directly to C1; the sulfur is doubly bonded to two oxygens and singly bonded to a hydroxyl oxygen, i.e., -S(=O)2-OH.  
2. Phosphoryl diethyl group: connect the phosphorus atom directly to C1;  the phosphorus is doubly bonded to one oxygen and singly bonded to two ethoxy oxygens, each bearing an unbranched -CH2-CH3 chain, i.e., -P(=O)(O-CH2-CH3)2.