Hello Bernd,
following the lines of Horst (or his "master in the background" 
)
data(min) = reduce ty_struc( init r = value ty_struc( col1 = nmax col2 = '' ) for m in itab next r = cond ty_struc( when r-col1 < m-col1 then r else m ) ).
The output class will then print the row with 5 and 'C'
cl_demo_output=>display( min ).
supposed we preceded the code with the usual declaratory bla-bla:
constants: nmax type i value cl_abap_math=>MAX_INT4. types: begin of ty_struc, col1 type i, col2 type c, end of ty_struc, ty_struc_tab type table of ty_struc with empty key. data(itab) = value ty_struc_tab( ( col1 = 10 col2 = 'A' ) ( col1 = 12 col2 = 'B' ) ( col1 = 5 col2 = 'C' ) ( col1 = 16 col2 = 'D' ) ).
I don't know whether there is a shorter expression for it than the above REDUCE term.