.beta.-D-Xylofuranoside, (3.beta.,4.beta., 5.alpha.,6.alpha.,15.beta.,24S)-3,4,6,15-tetrahydroxy-cholestan-24-yl 2-O-(2,4-di-O-methyl-.beta.-D-xylopyranosyl)- AIDS-168491 AIDS168491 Certonardoside H