The (l) stereoisomer cannot be converted directly into (dl) racemic mixture or a mixture with (ee),i.e. enantiomeric excess.
Instead, get ,e.g. 4-[(1R)-1-amino-2-hydroxyethyl]phenol hydrochloride available from Pharmblock Co. & treat it with a basic salt such as sodium acetate (to get rid of the stabilizing hydrochloride part). Immediately, apply oxidation using PCC (not any other oxidizing agent) & you will obtain d-4-hydoxy phenyl glycine.
Mix this product with the (l) stereoisomer in any ratio you want but at 50:50 you will have (dl)-hydroxyphenylglycine.
i) Racemisation take place in presence of enzymatic catalyst also .
ii) You could also refer the patent attached for racemisation of the aminoacid via chemical synthesis.
Normally you want to go the way around, i.e. to get optically pure compound from racemic. But, racemization of an amino acid like yours by no means of a problem as Abirami stated above. In fact some kinetic (or dynamic kinetic) resolution methods use in situ racemization in order to get the opposite enantiomer. Thus other than "racemize" enzymes reactive aldehydes or ketones (see above) can be used via an imine equilibrium. See further these additional links:https://www.google.hu/url?sa=t&rct=j&q=&esrc=s&source=web&cd=2&cad=rja&uact=8&ved=0CDIQFjAB&url=http%3A%2F%2Fwww.sciencedirect.com%2Fscience%2Farticle%2Fpii%2FS0040403900968163&ei=PVAVVND9MuTRywOHjYCACw&usg=AFQjCNFpKI0CJZqSmqKmfwFmbZdsvFs08Q&sig2=7fqShbNxOcPw9f4WHCzgog
http://books.google.hu/books?id=A10Vws4A_1YC&pg=PA210&lpg=PA210&dq=racemization+of+phenylglycine&source=bl&ots=bCRsUYGkGc&sig=Yl96T5C-RpxbM96-0cWkOX9dJmc&hl=en&sa=X&ei=Yk0VVNTNJML8ygPu7YHwCA&ved=0CKwBEOgBMBA
simply by heating L hydroxyl phenyl glycine with catalytic amount of salisaldehyde in acetic acid at 100deg for 2hrs yield nearly quantitative
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