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[reaction: see text] An enantioselective preparation of the four diastereomeric 3-amino-2,3,6-trideoxy-hexoses, key components of anthracycline antibiotics, has been developed. Sharpless catalytic asymmetric epoxidation of the (2E)-2,5-hexadien-1-ol, regioselective ring opening with azide, followed by convenient functional group transformations, afforded(More)
A new finite-state vector quantization (FSVQ) algorithm is developed based on state space optimization and the derailment prevention requirement. The proposed derailment-free FSVQ (DF-FSVQ) achieves good performance through (i) state space reduction, which allows a practical implementation of high-order FSVQ, and (ii) derailment free state transitions.(More)
with the natural isolate. The mechanism of the conjunctive coupling reaction is the subject of ongoing investigations, although the substrate scope (Figs. 2 and 3) gives clues about the process. The observation that electron-deficient arenes are less prone to migration is consistent with the mechanistic hypothesis put forward in Fig. 1E. According to this(More)
The reactions of aryl-stabilized sulfur ylides with organoboranes has been studied under a variety of conditions. At 5 or -78 degrees C, the reaction with Et3B gave a mixture of the first and second homologation products, but at -100 degrees C, only the first homologation product was obtained even with just 1.1 equiv of Et3B. Under these optimized(More)
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