Abstract:  Studies  on  complex  bioactive  natural  products will  be  presented  from  three aspects:  total  synthesis,  structure  elucidation  and  disease  diagnosis.  Natural  product mycolactone  A/B,  causative  toxin  of Buruli  ulcer disease,  can  undergo  photo-induced [3+2]  cycloaddition  reaction  to  give  photo-mycolactone  A/B which  has  significantly reduced  cytotoxicity.  The  highly  efficient,  cost/time  effective  and  operationally  simple fluorescent TLC  detection  method  can  detect  mycolactone  A/B  from a mouse  model, which  offers a  clinical diagnostic  tool  for Buruli  ulcer disease.  In  addition,  anti-aging natural product daumone was synthesized through de novo asymmetric total synthesis to provide the material for the biological activity study. The structure assignment of antimicrobial natural product cladospolide D was corrected by de novo total synthesis as well.