As highlighted above, the isomerization of D-G3P 1a to DHAP 20 catalyzed by TIM presented a problem for the the cascade to generate D-ribose-5-phosphate analogues. (Scheme 3). Phosphoenolpyruvate (PEP) has been previously shown to inhibit TIM and can also be used as a phosphate donor substrate for pyruvate kinase in order to implement an ATP recycling system. We reasoned that addition of phosphoenolpyruvate to the cascade could serve to both recycle ATP for the kinase step as well as increase overall conversion to product by inhibiting the formation of DHAP via TIM.