Branch butyrolactone

Crospovidone is a cross-linked homopolymer of A-vinyl-2-pyrrolidone. Acetylene and formaldehyde react to form butynediol. Hydrogenation and subsequent cyclodehydrogenation gives butyrolactone. The reaction of butyrolactone with ammonia produces pyrrolidone, which is vinylated with acetylene under pressure. The linear polymerization of the vinylpyrrolidone yields polyvinylpyrrolidone, a soluble binder, whereas the popcorn (branched) polymerization yields crospovidone, an insoluble... 

Five-membered lactones (y-butyrolactones) fused to carbohydrates have proven to be convenient synthons towards branched-chain sugars through opening of the lactone unit. Velaskes et al. [208] described the synthesis of y-butyrolactones... 

Figure 3 7-Butyrolactones in Streptomyces. The differences in chemical structure among the 7-butyrolactones are the length and branching of the acyl chain and the reduction state, either a keto or a hydroxyl group, at position 6.

The introduction of rhodium has allowed the development of processes which operate under much milder conditions and lower pressures, are highly selective, and avoid loss of alkene by hydrogenation. Although the catalyst is active at moderate temperature, plants are usually operated at 120°C to give a high n/iso (linear/ branched) ratio. The key to selectivity is the use of triphenylphosphine in large excess which leads to >95% straight chain anti-Markovnikov product. The process is used for the hydroformylation of propene to n-butyraldehyde, allyl alcohol to butanediol, and maleic anhydride to 1,4-butanediol, tetrahydrofuran, and y-butyrolactone. 

Branched-dd Sugars. - A ulosooic add derivative the squalastatin 1 analogue 42 (see Chapter 24), and die qwroanndated a-metfaylene-7-butyrolactone 43. 

The question arises whether these series of Q branches could be interpreted on a slightly anharmonic potential function rather than on a cosine function type of pseudo-rotation. For a low barrier ( 7.5 kJ mol ) the contribution to the entropy at 298 K of a hindered pseudo-rotator differs from that of a harmonic oscillator of the same frequency by 6 J K mol , which is certainly measurable. But for a high barrier ( 14.6 kJ mol ) the difference between the entropy contributions is 0.6 J K mol at 298 K and only 1.2 JK mol at 398 K. Therefore only for a low barrier can the two possibilities be distinguished by thermodynamic measurements. For Y-butyrolactone and ethylene carbonate the barriers are calculated to be 46 kJ mol and 75 kJ mol , respectively, which would negate the effect of pseudo-rotation at reasonable temperatures. Thus, in molecules with a sufficiently high barrier the motion can be treated as an ordinary vibration in which the puckering oscillates about a stable configuration. 

Branched-chain Sugars. - The silicon-tethered radical cyclisation adduct 14, 2 l-< -acetyl-2,4 5,6-di-0-isopropylidine-l-C-phenyl-D-g(ycgro-D-idc>-hexitol, the butyrolactones 15 and 16, the D-arabinose derived 17, 5 the diastereomerically pure disaccharide 18 and the a- and P-5 -phenyl analogues of daunomycin 19 and the C-linked disaccharide 20. ... 

Usually, both crystalline and amorphous phases are present in polymer electrolytes. Since only amorphous phases present high conductivity, plasticiser solvents are usually added to enhance the amorphous phase and thus the ionic conductivity. Here, propylene carbonate (PC), EC,y-butyrolactone (y-BL) and their binary mixtures are usually used as plasticiser solvents. Hie stereo structures of the polymer matrix molecules are given in Fig. 12.3, including linear, comb, crossing, star, hyper-branched and comb crosslinking. 

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