concatenating multiple shell command in a Makefile

[nike]

Hi I am trying to use the following code in a Makfile to change into a
directory and to execute Make all after testing the existence of a
file. However, Make does not seem to like the idea and report an
unexpected token.
all :
        @echo "in the main directory"
        @cd dir1  && if [-s toto]; then echo "toto existe";  else echo
"no
toto"; fi; && $(MAKE) all
could someone help me understanding how to execute multiple commands
on the same line? I have tried using backticks to quote the complete
line  or part of it  without success. Thanks for any help.
Guy