Here we examined the use of continuous flow conditions for the final assembly of eribulin mesylate aimed to avoid cryogenic condition. The diisobutylaluminum hydride reduction of ester 2 to aldehyde 3 and n-butyllithium-mediated coupling of aldehyde 3 and sulfone fragment 4 to produce sulfone-diol 5 were investigated. Under optimized continuous flow conditions, both reactions could be run at temperatures higher than those used under batch conditions. For the diisobutylaluminum hydride reduction of ester 2 to aldehyde 3, under optimized continuous flow conditions at −50 °C, aldehyde 3 was afforded with better HPLC area ratio than it was under batch conditions at −70 °C. Furthermore, continuous operation for 87 min afforded the same quality of 3 as was produced with a short-time operation (yield, 96.5%). For the n-butyllithium-mediated coupling of 3 and 4, under optimized continuous flow conditions at 10 °C, 5 was afforded with a better conversion rate than it was under batch conditions at −70 °C.

• Eisai Co. Ltd.

• API

1. API
2. continuous flow
3. Eribuline Mesylate
4. fluid dynamics
5. High-performance liquid chromatography
6. N-butyllithium-mediated coupling
7. Research Article
8. Transfer reactions