Nitrogen generators

Fig. 3. Pressure swing adsorption nitrogen generation system. CMS = carbon molecular sieve.

C-H activation a to nitrogen generates f3-amino acid derivatives (Figure 5). Therefore, the reaction can be considered to be a surrogate of the Mannich reaction. 

The only available evidence to support this is the fate of intermediates generated from the reaction of A-acyloxy-A-alkoxyamides with cysteine derivatives in methanol described in Section IV.C.3.b. The nucleophilic thiol reacts preferentially at the sulfur atom rather than at nitrogen, generating the hydroxamic ester and the disulfide (Scheme 24). 

Many nitrogen generator devices are commercially available to produce high purity gas in small amounts. In these, nitrogen is obtained from compressed air. It is separated from other air components by selective permeation through polymeric hollow fiber membranes after prefiltration. 

Dry diazodicyanoimidazole is highly explosive, however one can work safely with its solutions. When heated to 80°C in solution, 26 loses nitrogen, generating a highly electrophilic intermediate (Scheme 12) (73JA2695). Its chemical characteristics more resemble carbonium ions than aryne or carbodiimide. 

The reaction is completed within five minutes at room temperature. Thus, measurement of the volume of nitrogen generated can be used in amino add determinations. 

A third biosynthetic pathway to /-alanine 3 by oxidation of spermidine 13 and spermine 1 has been recently elucidated in yeast [17]. This reaction starts by transformation of L-methionine 15 to decarboxyadenosylmethionine (dcAdoMet, 16). The latter alkylates putrescine 12 at one or both nitrogens generating spermidine 13 and spermine 1 which are oxidized to 3-aminopropanal 14 and further to /-alanine (Scheme 1.6.4). 

Nitrogen generator (or equivalent cylinder with regulator) for heater/evaporator... 

A heater/evaporator with separate aluminium heating blocks (three sizes compatible with the vials glassware) and 6-position nitrogen purge concentrator with tubing for connection to nitrogen generator... 

Heater/evaporator to be used with pure nitrogen from a nitrogen generator (optional item) or a nitrogen cyhnder... 

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