In some embodiments, R1 is an alkenyl group, i.e., (???CH???CH)n???R4, wherein n is an integer from 0 to 10, and R4 is a halogen such as is I??? or Br???, CN??? or mercury; wherein R2 is H and R3 is ???OH; wherein R2 is OH and R3 is H; wherein R2 and R3 are H; or wherein R2 and R3 are OH.