Hydroxypropionic limitations

The activity of propionyl CoA carboxylase in lymphocytes falls, and the activation of the apoenzyme on incubation with biotin rises, in patients receiving total parenteral nutrition before there is any change in the plasma concentration of biotin (Velazquez et al., 1990). In experimental animals, the activity of lymphocyte propionyl CoA carboxylase falls early during biotin depletion, at the same time as the activity of the hepatic enzyme. There is not the expected increase in urinary excretion of hydroxypropionic acid, presumably because propionyl CoA carboxylase is not rate-limiting for propionate metabolism (Mock and Mock, 2002). 

Biodegradable Polymers Properties, Possibilities, and Limits Considering the Synthesis, Processing, and Application of Poly(2-Hydroxypropionic Acid) and Poly(3-Hydroxybutyric Acid)... 

We next turned our attention to the Clark zirconium allylation for the synthesis of C8-C9 bond (Scheme 6). Clark had previously shown that in s(tM-generated allyl zirconium nucleophiles could selectively produce anfz-hydroxypropionates of a variety of aliphatic and aromatic aldehydes. In our lab, we found that reaction of aldehyde 15 with the same allyl zirconium nucleophile did selectively generate anti-hydroxypropionates. Unfortunately, the epoxide failed to control the facial selectivity of this addition thus, a 1 1 mixture of separable diastereomers 18 and 19 was formed. This reaction represents our first successful, albeit limited, synthesis of the desired intermediate 18. We next attempted to optimize the output of diastereomer 18 by modifying the Clark reaction conditions defined as THF or PhCH3 solvent with no additives. 

Because at that time we had access to only a limited supply of aldehyde 15, we decided to optimize the Clark allylation using the cinnamaldehyde-based model system. We found that, by using external Lewis acids in nonpolar solvents (PhCH3, Et20 or CH2CI2), the stereochemical outcome of the Clark allylation could be reversed to selectively produce 5> n-hydroxypropionates. Application of the... 

Poly(3HB-C6>-3HP), produced by R. eutropha and A. latus as noted above, has also been synthesized by a soil isolate of Methylobacterium [117]. In nitrogen-limited cultures containing methanol as the main carbon source (0.5% (v/v)), the addition of 3-hydroxypropionate led to accumulation of the copolyester. The 3HP fraction in the polymer could exceed 10 mol%, but total copolymer content in the cell was always below 12%. 

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