4) When the radical weaponry of each calicheamicin γ 1 I is activated, it removes a
hydrogen atom from the backbone of DNA.
5) This leaves the DNA molecule as an unstable radical intermediate, which in turn
results in double strand cleavage of the DNA and cell death.NHHO
S S SMe SSSO CO 2 MeH OSugar- nucleophilic
attack - conjugate
addition N
H
HO O
H CO 2 MeO SugarBergman
cycloaromatizationNHHO O
H CO 2 MeO Sugarcalicheamicin γ 1 INHHO O
H CO 2 MeO SugarDNA
DNA
diradicalO 2 DNA double
strand cleavage- The total synthesis of calicheamicin γ 1 I by the research group of K. C. Nicolaou
(The Scripps Research Institute, University of California, San Diego) represents a
stunning achievement in synthetic organic chemistry.