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Effects of Neighbouring Groups and of Substituents in Organic Sulfur Compounds.

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Effects of Neighbouring Groups and of
Substituents in Organic Sulfur Compounds
K. D . Gundermann, Munster/Westf. (Germany)
The intermediate formation of ethylenesulfonium ions of the
type
H2C-CH-CN
(AS’
(COOR)
R
explains why the addition of alkylsulfenyl chlorides (RSCI)
to derivatives of acrylic acid [I] gives not only a-alkylmercapto-P-chloropropionic acid derivatives, which are to be expected on the basis of the polarity of the reactants, but isoacid derivatives as
meric a-chloro-P-alkylmercaptopropionic
well. On the other hand, cc-dialkylaminoacrylic acid derivatives, which should react like the corresponding thiosther
derivatives, could not be made to add mercaptans, malonic
ester or diazomethane in a preparatively useful manner.
Considering the capability of the S atom to undergo octet
expansion [2],the following extreme mesomeric structures,
which make possible a polar mechanism for “head-to-head’
dimerization, were discussed.
(COOR)
HS=C-CN
I
cf
SR
(f)
(COOR)
HsC-C-CN
II
tf
(-1SR
(4 (COOR)
H-J-C-CN
It
(t)SR
Attempts to propare a-nitroacrylic esters (in order to study
the effect of a particularly strong electron-attracting substituent in the a-position of the acrylic acid bond system)
from cr-bromo-P-methoxypropionic ester according to the
method of Kornblum [3]lead to cr,a’-dinitro-a-methoxymethylglutaric ester. This compound arises by a Michael
ester to a-nitroacrylic
addition of cc-nitro-P-methoxypropionic
ester, which is formed in the course of the reaction; its
structure was proved by energetic reduction to cc-methyI-a,cc’diaminoglutaric acid.
[GDCh-Ortsverband Krefeld (Germany), April 5 th, 19621
[VB 580/31 IE]
[l] H. Brintzinger and M . Langheck, Chem. Ber. 87, 325 (1954).
[2] G. Cilento, Chem. Revs. 60, 147 (1960).
[3]N. Kornblum, J. Amer. chem. SOC.79, 2507 (1957).
From optical rotation measurements, it can be shown that in
dimethylformamide and methanol, I occurs essentially as a
helix. Addition of water reduces the portion of the helical
structure. In distilled water, the helical structure amounts to
only SO%, and addition of urea results in complete “denaturation” of the molecule.
With polyproline, the presence in Escherichia coli of a previously unknown proline iminopeptidase was demonstrated.
The enzyme splits the bond between the imino nitrogen of the
five-membered ring and the carbonyl group of the next pyroline residue. Polyalanyl ribonuclease containing 40 alanine
residues per molecule and polyalanyl trypsin are as active
enzymatically as the native enzymes. If all four disulfide
bridges in polyalanyi ribonuclease are reduced and reoxidized, all the enzymatic activity is regained. Polyalanyl ribonuclease also has three free amino groups in the RNase chain
(unchanged RNase has 11). Among these three free amino
groups is the s-amino group of lysine residue No. 41, which
is considered to be part of the active center.
Gelatin is normally a very weak antigzn. If this protein is condensed with tyrosine, tryptophan, phenylalanine, cyclohexylalanine, orcysteine peptides, it becomes a strong antigen. At a
tyrosine content of 2 % (w/w), primarily antibodies against
gelatin result. With a tyrosine content of 10 %, the antibodies
are almost completely directed against the polytyrosyl residues attached to the gelatin. Since in this case gelatin apparently only plays the role of an inert carrier, it was replaced
by multichain poly-(oL-alanine). Tyrosylation of this polypeptide resulted in a strong antigen. It produced antibodies
primarily directed against tyrosine. Among numerous linear
and branched polypeptides, consisting of one or more of the
amino acids tyrosine, glutamic acid, lysine, or alanine, only
those containing tyrosine proved tu be antigens. Thus, these
synthetic polypeptides allow immunological itivestigations on
well-defined models which can be altered in a controlled
fashion.
[GDCh-Ortsverband Freiburg-Siidbaden (Germany),
May 18th, 19621
[VB 587/33 IE]
Ternary Compounds of Mercury Halides with
Elements of Groups 5B and 6B
H . PuR,Kiel (Germany)
Synthetic Polypeptides as Models for Proteins
M . Sela, Rehovoth (Israel)
Of the many synthesesfor poly(a-amino acids), polymerization
of anhydrides of N carboxy-a-amino acids (Leuchs anhydrides) proved particularly advantageous. This procedure yields
high-molecular weight materials with very narrow distribution of molecular weights. The polymerization succeeds even
in aqueous solution. With polyvalent amines (e.g. polylysine)
as initiators, branched poly(amino acids) are obtained. By the
same process, proteins can be converted into polypeptidyl
proteins.
Simple water-soluble protein models should help in the study
of the helical content of proteins in aqueous solution. If 1,3propanolamine is treated with poly-(y-benzyl-L-glutamate), a
product designated as poly-[NJ-(3-hydroxypropyl)-~-glutamine] (I) results. It is soluble in water and in several organic
solvents and contains neither free amino groups nor free carboxyl groups in its chain.
CO--NH-(CH&-OH
I”
Angew. Chem. internat. Edit.
1 VoI. I
(1962) No. 7
The reaction of PH3 with HgC12 yields various different precipitates depending on the experimental conditions:
a) in aqueous solutions at pH < 1, in ether, dioxan, or tetrahydrofuran, a yellow substance HgjPC13 is obtained
b) in aqueous solutions at p H > 5 or in pyridine, a black
precipitate in which Hg:P = 3:2, frequently contaminated
with elemental mercury, is formed
c) in aqueous solutions at pH 2-3, as well as in methanol,
ethanol, or isopropanol, mixtures of the above two substances of brown appearance are obtained.
All the precipitates are amorphous, judging by X ray analysis. From its properties and reactions, it is concluded that
Hg3PC13, analogous to the chloride of Millon’s base
(Hg2N)CI, has a spatial lattice cation of 2-coordinate mercury and 4-coordinate phosphorus, the positive charge being
balanced by HgC13Qions, i.e. (HgzP)(HgCI3).
When phosphonium halides are allowed to react with salts of
mercury and cadmium, PH4HgBr3, PH4HgI3, PH4CdBr3,
and PH4CdI3 are obtained. These substances are very sensitive towards moisture and heat. PH4HgBr3 crystals have the
perovskite structure.
By annealing mercurous halides with red phosphorus or
arsenic, the following almost insoluble and very stable compounds were formed: Hg2PC12, HgzAsClz, HgZPBrz,
Hg2AsBr2, Hg?P2Cl2, Hg3AsiCl2, and Hg4AszC13. The latter
compound crystallizi% in the cubic system, the others in the
41 1
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effect, compounds, neighbouring, group, organiz, sulfur, substituents
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