Trovafloxacin, synthesis

This reaction is used for a total synthesis of trovafloxacin (Scheme 5.18).120... 

The first quinolone, nalidixic acid, was isolated as a byproduct of the synthesis of chloroquine. It has been available for the treatment of urinary tract infections for many years. The introduction of fluorinated 4-quinolones, such as ciprofloxacin (Cipro), moxifloxacin (Avelox), and gatifloxacin (Tequin) represents a particularly important therapeutic advance because these agents have broad antimicrobial activity and are effective after oral administration for the treatment of a wide variety of infectious diseases. Relatively few side effects appear to accompany the use of these fluoroquinolones, and microbial resistance to their action does not develop rapidly. Rare and potentially fatal side effects, however, have resulted in the withdrawal from the market of temafloxacin (immune hemolytic anemia), trovafloxacin... 

VUsmaier E, Goerz T (1998) Diastereoselective syntheses of iV-protected derivatives of la,5a,6/ -6-amino-3-azabicyclo[3.1.0]hexane a route to trovafloxacin 6/ -diastereomer. Synthesis 1998(5) 739-744... 

Norris T, Braish T, Butters M, DeVries K, Hawkins J, Massett S, Rose P, Santafianos D, Sklavounos C (2000) Synthesis of trovafloxacin using various (la,5a,6a)-3-azabicyclo[3.1.0] hexane derivatives. J Chem Soc Perkin Trans 1 2000 1615-1622... 

The conversion of 24.37 to a cyclopropane in the synthesis of the antibiotic trovafloxacin (a very controversial compound, the use of which is now largely discontinued) was required. The original synthesis was accomplished by a process that was considered to be too hazardous on a large scale, and the process shown in the following was used. Propose a mechanism for this process. 

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