\chemfig{
                   HO% 16
          -[:60,,2]% 13
           =_[:120]% 12
             -[:60]% 11
                 =_% 8
             -[:60]% 7
                  -% 10
            -[:300]% 1
                  -% 6
           =_[:300]% 5
            -[:240]% 4
                      (
            -[:300,,,1]OH% 17
                      )
            -[:180]% 3
            -[:120]% 2
                      (
                 -[:60]% -> 1
                      )
                      (
                -[:180]% 9
                          (
                    -[:120]% -> 8
                          )
               =_[:240]% 14
                          (
            -[:327.1,1.233]O% 15
             -[:34.8,1.174]% -> 3
                          )
                -[:180]% -> 13
                      )
    -[:123.3,0.928]% 19
     -[:89.9,1.239]% 20
     -[:30.1,1.163]N% 18
                      (
                -[:240]% -> 10
                      )
           -[:37.5]% 21
}

.
