Foslevodopa (FLD, levodopa 4′-monophosphate, 3) and foscarbidopa (FCD, carbidopa 4′-monophosphate, 4) were identified as water-soluble prodrugs of levodopa (LD, 1) and carbidopa (CD, 2), respectively, which are useful for the treatment of Parkinson’s disease. Herein, we describe asymmetric syntheses of FLD (3) and FCD (4) drug substances and their manufacture at pilot scale. The synthesis of FLD (3) employs a Horner–Wadsworth–Emmons olefination reaction followed by enantioselective hydrogenation of the double bond as key steps to introduce the α-amino acid moiety with the desired stereochemistry. The synthesis of FCD (4) features a Mizoroki–Heck reaction followed by enantioselective hydrazination to install the quaternary chiral center bearing a hydrazine moiety.

IntroductionChemical industries are constantly in search of an expeditious and environmentally benign method for producing chiral synthons. Ketoreductases have been used as catalysts for enantioselective conversion of desired prochiral ketones to their corresponding alcohol. We chose reported promiscuous ketoreductases belonging to different protein families and expressed them in E. coli to evaluate their ability as whole-cell catalysts for obtaining chiral alcohol intermediates of pharmaceutical importance. Apart from establishing a method to produce high value (S)-specific alcohols that have not been evaluated before, we propose an in silico analysis procedure to predict product chirality.ResultsSix enzymes originating from Sulfolobus sulfotaricus, Zygosaccharomyces rouxii, Hansenula polymorpha, Corynebacterium sp. ST-10, Synechococcus sp. PCC 7942 and Bacillus sp. ECU0013 with reported efficient activity for dissimilar substrates are compared here to arrive at an optimal enzyme for the method. Whole–cell catalysis of ketone intermediates for drugs like Aprepitant, Sitagliptin and Dolastatin using E. coli over-expressing these enzymes yielded (S)-specific chiral alcohols. We explain this chiral specificity for the best-performing enzyme, i.e., Z. rouxii ketoreductase using in silico modelling and MD simulations. This rationale was applied to five additional ketones that are used in the synthesis of Crizotinib, MA-20565 (an antifungal agent), Sulopenem, Rivastigmine, Talampanel and Barnidipine and predicted the yield of (S) enantiomers. Experimental evaluation matched the in silico analysis wherein ~ 95% (S)-specific alcohol with a chemical yield of 23–79% was obtained through biotransformation. Further, the cofactor re-cycling was optimized by switching the carbon source from glucose to sorbitol that improved the chemical yield to 85–99%.ConclusionsHere, we present a strategy to synthesize pharmaceutically relevant chiral alcohols by ketoreductases using a cofactor balanced whole-cell catalysis scheme that is useful for the industry. Based on the results obtained in these trials, Zygosaccharomyces rouxii ketoreductase was identified as a proficient enzyme to obtain (S)-specific alcohols from their respective ketones. The whole–cell catalyst when combined with nutrient modulation of using sorbitol as a carbon source helped obtain high enantiomeric and chemical yield.Electronic supplementary materialThe online version of this article (10.1186/s12934-018-1036-2) contains supplementary material, which is available to authorized users.

Tumor angiogenesis has become an important target for antitumor therapy, with most current therapies aimed at blocking the vascular endothelial growth factor (VEGF) pathway. The VEGF and its receptors have been implicated as key factors in tumor angiogenesis and are major targets in cancer therapy. A series of aryl‐modified benzoylamino‐N‐(5,6‐dimethoxy‐1H‐benzoimidazol‐2‐yl)‐heteroamides were synthesized from 2‐amino‐5,6‐dimethoxy benzimidazole and aryl‐substituted benzoylamino hetero acids. The new compounds were tested for inhibition of VEGF receptors I and II (VEGFR‐1 and VEGFR‐2). Compound 6e displayed VEGFR‐2 inhibitory activity with a 50% inhibition concentration value as low as 0.020 μM in a homogeneous time‐resolved fluorescence enzymatic assay. VEGFR‐2 active compounds display good activity against VEGFR‐1 as well.

The sprouting of new blood vessels, or angiogenesis, is necessary for any solid tumor to grow large enough to cause life‐threatening disease. Vascular endothelial growth factor (VEGF) is one of the key promoters of tumor‐induced angiogenesis. Inhibition of the VEGF signaling pathway has emerged as one of the most promising new approaches for cancer therapy. A series of 6,7‐dimethoxy‐quinazolin‐4‐yl‐amino‐nicotinamides were synthesized and evaluated as antagonists of VEGF receptor II (VEGFR‐2). Many compounds display VEGFR‐2 inhibitory activity, and compound 7a was found to be a potent inhibitor of VEGFR‐2 in an homogeneous time‐resolved fluorescence enzymatic assay with an IC50 as low as 48 nM (comparable activity to ZD‐6474).

The identification of agents with antiproliferative activity against endothelial cells has significant value for the treatment of many angiogenesis‐dependent pathologies. The vascular endothelial growth factor (VEGF) and its receptors have been implicated as key factors in tumor angiogenesis and are major targets in cancer therapy. A series of novel 6,7‐dimethoxy‐quinazolin‐4‐yl‐amino‐thiophene‐2‐carboxamides were synthesized and evaluated as antagonists of VEGFR‐1 and VEGFR‐2. More specifically, several analogues exhibited low micromolar to nanomolar potency in the inhibition of VEGFR‐1 and VEGFR‐2. The most potent compound in this series, compound 7b, was found to be a potent inhibitor of VEGFR‐2 in a homogeneous time‐resolved fluorescence enzymatic assay with an IC50 as low as 87 nm.