Screening of various catalyst loadings (1 10 mol-%; see the Supporting Information) revealed that 4 mol-% gave the highest but a still unsatisfactory yield (entry 2) as higher catalyst loadings led to increased byproduct formation (C-3 arylation, debromination, and homocoupling of 4-bromoanisole).
P.S. – One year after, bad news: the delicious new pepper variety, as good and safe as it was, has given unsatisfactory yield results, some 15 20% lower than its competitors which are already on the market.
Initial attempts to activate the protected amino acids for coupling using PyBop and HOBt provided unsatisfactory yields; however, a brief screening of activating agents revealed that Goodman's reagent (DEPBT) provided the desired PLMs in good yield [41], [42].
Although these methods may be effective, some of them have relatively long reaction times and unsatisfactory yields.
Majority of directly expressed AMPs, such as LL-37 (Hong et al. 2007), CecropinAD (Jin et al. 2009), and N2 (Yang et al. 2016), showed unsatisfactory yields.
However, all these manufacturing processes exhibited partial disadvantages like unsatisfactory yields, formation of dangerous by-products or poorly accessible or fossil fuel derived raw materials (Thewalt et al. 1980, Felder et al. 1987).
However, many of these methods suffer from disadvantages such as long reaction times [9, 10], unsatisfactory yields, harsh reaction conditions [8], expensive reagents [11, 13, 19], hazardous and toxic solvents or catalysts [17, 18], tedious work-up, formation of polymeric by-products of the dihydropyran (DHP) and isomerization.
Isolating the desired (PCB 2C2 dumbbell in sufficient purity from the complex reaction mixture however proved difficult and gave unsatisfactory yields (<10 %).
The request for Congress to extend Mueller's 10-year term follows a problematic search for his replacement, which administration officials said Thursday had yielded an unsatisfactory shortlist of candidates.
