The authors have examined the structure of the prolyldiketopiperazine “B” which was previously
(1) found in the sclerotia and saprophytic cultures of
Elymus-type ergot fungus.
From the physico- and spectro-chemical data, it was found that “B” must be constituted from D-proline and a new L-amino acid “X” which was presumed to be L-homoleucine.
“X” was obtained in crystalline form from the acid hydrolyzate of “B”; C
7H
15NO
2, mp 211_??_215°C (decomp.), [α]
25D+25°(
c=0.2, 6 N HCl). On the other hand, the authentic L-homoleucine was prepared by treating the synthetic 5-methyl-2-amino-hexanoic acid (D, L-homoleucine) of S. David and J. -C. Fisher
(5) with D-amino acid oxidase (pig kidney, Miles Lab., Inc).
It was found that “X” is identical in all respects with the authentic L-homoleucine, and by this finding, it was confirmed that “B” is nothing but a new compound, L-homoleucyl-D-proline-lactam.
From the present result together with that obtained in previous experiment,
(6) the structures of two peptide-type ergot alkaloids, “P
1” (ergohexine) and “P
2” (ergoheptine) could be proposed for the first time.
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