192 



SHIRO AKABORI 



, — CHi— O 

 =/ I COCl» HQ t 

 CHï *" ~^ 



I 

 CH— NH2 



I 

 COOH 



>— CHî— O 



CH: 



PH4I NH3— Na 





OH 



I 



CH2 

 I 

 — NH— CH— CO— 



" : 37 



CH2 



I 



— NH— CH— CO- 



6n HCl 



CO2 



CH— NH 



I 



CO — o 



CO 



5NNaOH 



>- 



/~ - — CH-.SH 

 room temp. 



S-Benzylcysteine 



Hydrolysis 



-*- Serine 



Alanine 



Fig. 2. 



— CH;— O 



CHî 



I 



— NH— CH— CO— 



CH2 

 -NH— C— CO— 



"i 



The formation of aspartyl residue in the fore-protein is also most likely to 

 have occurred by a series of reactions shown in Fig. 3. The experiment to test 

 this possibiHty was carried out by employing polydehydroalanine synthesized 

 by Sakakibara from carbobenzoxy-dehydroalanine as shown in the figure. 



NH NH NH NH NH 



I CHjO I HCN I I I 



CH2 — -^C = CH2 *-CH— CH2— CN > CH— CH2— CONH2-' CH— CH2— COOH 



CO 



CO 



CH2 



C— COOH 



CO 



CO 



I AspCNHa). 



CO 

 I Asp. 



PCU 



CHz 



-CO 



— C02 



O 



NH— CO— O— CHa— ^' 



> 



NH — CO 



Asp. 6N-HCI 



Ala. 6n~HCI 



CH>— CN 



— NH— CH— CO- 



and 



CH:. 

 1 

 — NH— C— CO— 



I 

 CN 



HCN/ 



Scr. 



Poly-Dehydroalanine 



CH2 



1, 



C 



/ \ 

 -NH CO— . 



ti ■ 100 



- tl"=0 



CH2— OH 



I 

 CH 



— NH., CO- 



tlCHoO 



Gly. [— NH— CHî— CO— ] „ 

 Fig. 3. Formation of aspartic acid. 



i 



Polydehydroalanine is a Ught-brown, amorphous powder, which is soluble in 

 water and formic acid but not in alcohols. This polymer was dissolved in water 

 with potassium cyanide and kept at 20-25^ for 20 hours in a sealed tube and 

 then hydrolysed by hydrochloric acid. The hydrolysate was chromatographed 



