pdftk is not very good for this task. The handles can be only one letter and must be an uppercase letter, so only A-Z is possible.
But it can be done by making a temporary directory, extract page 1 of every PDF into a separate file in that directory, and then join all those PDF files into a big one. Here is a little script that does the job:
#Set the filename on the line below:
#Here is the temporary directory:
for name in *.pdf ; do
pdftk "A=$name" cat A1 output "$tempdir/$name"
pdftk $tempdir/*.pdf cat output "$DESTINATION"
rm -r $tempdir