No abstract

Thermolytic rearrangement of the diphenyl-propargylallene [3,3-(biphenyl-2,2 0 -diyl)-1-phenyl-1-{9-[(phenylethynyl]-9H-fluorenyl}allene], 9, yields the bis-fluorenyliden-bis-allene 10, which undergoes electrocyclization to form 3,4-di(fluorenyliden)-1,2-diphenylcyclobutene, 12, in which the overlapping fluorenylidenes give rise to C 2 symmetry. The propargylallene 9 reacts with iron carbonyls to form 15, in which an (η 5 -fluorenyl)Fe(CO) 2 moiety is linked both directly and via a bridging dC(Ph)-C(dO)linkage to a cyclobutene ring possessing a phenyl group and a spiro-bonded fluorenyl substituent. The diphenyl-propargylallene 9 and its bis(trimethylsilyl)propargylallene analogue, 2, each react with Co 2 (CO) 8 to furnish the corresponding alkyne-Co 2 (CO) 6 complexes 14 and 13, respectively. Treatment of the diphenyl-propargylallene 9 or the mono(trimethylsilyl)propargylallene 25 with silver nitrate in methanol or water effects cyclization of the allene onto the alkyne to furnish a cyclopentadiene that bears a 9-methoxy-or 9-hydroxy-fluorenyl substituent and is also spiro-bonded to a second fluorenyl moiety. The reaction of 3,3-(biphenyl-2,2 0 -diyl)-1-bromo-1-phenylallene with Fe 2 (CO) 9 yields the novel bicyclo-[3.2.0]heptadienone 21, which possesses two phenyl groups and is also spiro-linked to two fluorenyl fragments. All new compounds were characterized by NMR spectroscopy and X-ray crystallography.

When fermenting milk, lactic bacteria convert part of α- and β-lactoses into d- and l- lactic acids, causing a pH decrease responsible for casein coagulation. Lactic acid monitoring during fermentation is essential for the control of dairy gel textural and organoleptic properties, and is a way to evaluate strain efficiency. Currently, titrations are used to follow the quantity of acids formed during jellification of milk but they are not specific to lactic acid. An analytical method without the use of any reagent was investigated to quantify lactic acid during milk fermentation: in situ quantitative proton nuclear magnetic resonance spectroscopy. Two methods using in situ quantitative proton nuclear magnetic resonance spectroscopy were compared: (1) d- and l-lactic acids content determination, using the resonance of their methyl protons, showing an increase from 2.06 ± 0.02 to 8.16 ± 0.74 g/L during 240 min of fermentation; and (2) the determination of the α- and β-lactoses content, decreasing from 42.68 ± 0.02 to 30.76 ± 1.75 g/L for the same fermentation duration. The ratio between the molar concentrations of produced lactic acids and consumed lactoses enabled cross-validation, as the value (2.02 ± 0.18) is consistent with lactic acid bacteria metabolism.