R13
ATOM  C1   C2   C3   C4   C5   C6   C7   C8   C9   C10
ATOM  C11  C12  C13  C14  C15  C16  C17  C18  C19  C20
ATOM  C21  C22  C23  O1   O2 
CONNECT -  C1   C2  C3  C4  C5  C6  C7  C8  C9  C10  C1  C20 +
CONNECT  C1   C21
CONNECT  C4   C18
CONNECT  C4   C19
CONNECT  C5   C10
CONNECT  C8   C11  C12  C13  C14  C15  C16  C17  O1
CONNECT  C11  C22
CONNECT  C15  C23
CONNECT  C17  O2