documentclass{article}
usepackage{tikz-cd,amsmath,amssymb}

begin{document}

begin{tikzcd}
1 arrow[rrd, "alpha"] &  &  &  &  \
 &  & 3 &  & 4 arrow[ll, "gamma"'] \
2 arrow[rru, "beta"] &  &  &  &
end{tikzcd}

end{document}