... B1b; avermectin B1a; (10E,14E,16E,22Z)-(1R,4S,5'S,6S,6'R,8R,12S,13S,20R,21R,24S)-6 ... '-[(S)-sec-butyl]-21,24-dihydroxy-5',11,13,22- ... (i) mixture with (10E,14E,16E,22Z)-(1R,4S,5'S,6S,6'R,8R,12S,13S,20R,21R,24S)-21 ... 29(7)55-37/h12-15,17-19,25-26,28,30-31,33-45,49-50,52H,11,16,20- ... 11+,26-14+,31-13+/t25-,26+,28+,30+,31+,33-,34+,35+,36+,37+,38+,39+,40-,41+,42+,43-,44+,45 ...