- A study on the racemization step in the synthesis of pyrrolidinols via cyclic α-hydroxyimides
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Analytical HPLC methods for the determination of the enantiomeric excess of N-protected malimides 1 as well as the corresponding pyrrolidinol 5 and tartarimides 2 and 3 have been established. On this basis, a study to reveal the racemization step in the synthesis of pyrrolidinols from α-hydroxyacids, via chiral cyclic α-hydroxyimides, has been undertaken. It was confirmed that the known, one-step method for the synthesis of the N-protected chiral cyclic imides from α-hydroxydiacids proceeded with little racemization, and partial racemization has been proven to occur during the reduction of the resultant imide 1a with LAH to yield the corresponding pyrrolidinol 5. Conditions have been defined in order to avoid racemization in the LAH reduction step.
- Zheng, Jin-Li,Liu, Hui,Zhang, Yu-Feng,Zhao, Wei,Tong, Jin-Shuan,Ruan, Yuan-Ping,Huang, Pei-Qiang
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scheme or table
p. 257 - 263
(2011/05/12)
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- A versatile approach to pyrrolidine azasugars and homoazasugars based on a highly diastereoselective reductive benzyloxymethylation of protected tartarimide
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A highly diastereoselective synthesis of enantio-enriched all trans-3,4-dibenzyloxyl-5-benzyloxymethyl-2-pyrrolidinone 13a was developed based on SmI2-mediated benzyloxymethylation of O,O′-dibenzyltartarimide. The versatility of 13a and its antipode as the key building blocks for the asymmetric synthesis of pyrrolidine azasugars and homoazasugars has been demonstrated by elaborating them into naturally occurring DAB 1 (1), LAB 1 (2), N-hydroxyethyl-DAB 1 (4), 6-deoxy-DMDP 7, and 5-epi-radicamine B 36 as well as the reductive ring-opening product 35.
- Zhou, Xiang,Liu, Wen-Jun,Ye, Jian-Liang,Huang, Pei-Qiang
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p. 6346 - 6357
(2008/02/05)
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