Cron, command is working, but not in cron, missing }

Question

I have this cronjob.

50 15 * * * cd /var/www/html; for i in $(ls -d */); do tar zcvf ${i%%/}.tar.gz $i; done

But it shows me this.

/bin/sh: 1: Syntax error: Missing '}'

But when I run this command from command line directly, it works.

Where is the problem?

Thanks.