The following code should give you results close to what you want:
res = sscanf(str1,'%*[^0123456789]%d')
The idea is that sscanf will try to match all the strings specified, and if it doesn't find a match, then it returns what is found. So, when you use '%d', since the first character in the string is a letter and not a number, it doesn't find a match, and returns nothing.
In the code above, the first element is looking for anything that doesn't match the numbers 0-9. The carat in the beginning indicates a non-match. The asterisk indicates that you don't want to save that information in the output. So, it looks for non-numbers then numbers alternating until the end of the string and only saves the numbers. The documentation for textscan explains it better.
