The Senecio Alkaloids. Part 2

15 Pages·2016·1.17 MB·English

Unde-rstepoorL Joui'IUt! uf ~·eter£nary Sf'lenn; and A._n·£mal ind-ustry,
Tlolwne 14, Numbers 1 and:!, l unuary and A7;ril, 1940.
Printed i" the l'n ion of Sou tit Africa by the
(;01-ernmcnt Printe1·. Pretoria.
The Senecio Alkaloids. Part 2 : Hydrogena
tion, Hydrolysis and Structural Results of
lsatidine.
By H. L. DE \\' AA L. Seetion of Pha rlll<lt·olog-y a n<l 'l'oxico I ng·y,
() 11 derstepoort.
Lx the first Jl<lpt•r of this ~erie:; (de \Yaal, 193f.l) the isolation a11d
ehen1ieal propt·rtie:; as ~~-ell a,; the results of thP preliminar~- hy<lroly:ii,;
:uul u£ t lte hydrog-enation of the alka l oi<l i ,;;1 tid i ne ,,-t:.r <> recorrlt>d.
'l'hi;; alk;tloid is the aeti,·e prin .. iple particularly of Sr,tu'Cto isatideus
hut 11·a,; abo fo11111l to lw pre,;ent in Yery mu<;h lilllHll<-•r cptantit-ies in
S. retrorws ]).C. [t '""s then fuun1l that wl11•n isaticline was hydro
g-ellated ill tl1P pre::;eJI(·e of platinum dioxide four molt·<·ulp,; of
hydrogen \\'ere cousumed, ,,-bich at the time •·ould not })(' p:-;pbinrd.
Continuo11:; •·fl'ort:i lwn-• :iincr !eel to the n·pe<t!t·cl and f:1ciliL-Ltt·<l
isol.1tion of th .. rrdutTd. I'OillpOIIIHl in thP crystalline fonn, :llltl thi,;
as \Yell <IS son It' ut hrr ,;( rudural rP:itllts on i:i;t! itline <ll'l' II ll\\' n·portPtl
upon.
T/,p .\'ot·utP of the 1/ydrnuenniPrl ,..;ulJstmu·l'.
'l'he hydi·og-eJiatioJI of i:;at-itline (PtOJ in half-nm·mnl or nol·mnl
hyclrochloric :1eicl ~olution !t·acls to the coi1S1ll11ption of four molt•t·ull·:i
of hydrogen flll' one molec·u le of tlw alb loicl. The n•,mlti ng h~·dro­
g·enated prorlud has hPf'll i,;o]ate<l hnth <IS the free hasc and as its
hydrochloride. Both are laeYo-rotator_,-, n_,-:i(a]JinP _-;ub:-;tance:; ant!
the :maly+si s l'Pvealed a sh-iking- phPnOlliPnon. l,;atidinr, (',RI-l0,,KO,
took up moler·ules of !t_,·clro"·en. thPn SJJiit. nff ont- mnlecnle of
\\'::tter, so th;tt·. thr T'1'S11lt-ing- h:ISP has the fnnnula. C IL"O.,K or
18
(\ 8li3,00X.Il('] for it~ h~·tlror·lilnridt·, thus:
+
C H N0 4Tf (Cisi-I:lal\'07]
18 25 7 2
[C1sfl,~3~07] - H 20 ClsH31~0G-
0ct-ahydro-a :1 h Hlro-is;u-id inc.
I I .11d ro 1.'1-' Is o j Octu /, yd m-nn/1 .IJd t·o-iso 1/rl i 11 e.
\\/hen or:tahydro-anhyuro--isatidine was hydrolysed ~~-it!t barium
hydroxide, the split in the moleeule occmTed at the same place as is
the case "i th i sa tidine, i.e. a basic fission product containing- 8 carbo 11
433
THE SENECIO AL1 \ALOIDS.
atoms was prouuced, vill. C H,0 K, a tetrahydro-deri1·ative of
8 3
isatinecine (C H "0 Barger and his associates (1932) hyd1·o
8 1 3::\").
genated retrorsine (as it,; diacetyl clerinttive) and found that only two
molecules of hydrogen ,,·ere u,;ed. They failE>cl to isolate the
hydrogenated substance but isolnted hom the h~·drolysis mixture a
base C H",O'N (retronecine has the formula C,H",0 X ), ,,-hich the)·
8 2
nnmed rehone('anol. Our base, C H ,0 :1, conhilmtes ne11· infonna
8 1 3
tion to,,·ards the chemistry of the SenE>cio alka loi<ls. a hy<l rogenated
base having been obtained "·ithout any loss of oxygen atoms. Tlw
hydrogen has therefor!:' saturatecl mo,;t likely ethylE>nic or hen11yleni(:
double bonds onl:'i- and the possi hili ty of an enol i <·-CO-CH -g·ronpi n g-
2
~~;; sngo·ested for retrorsine must lw ruled out for is<~tidine. ·
The F1tnction of the O:vygen Atoms 1:n lsatinecine, Isatinecir Acid
and Isotidine.
It must be accepted meanwhile that isatinecine C'sH, 0 N, has
3 3
three reactive hydrogen atoms although this could not he acetyla.ted
or cletermined (ZereiYitinoff), in the latter case 1lue to its insolubility
in Pitlter pyridine or anisole.
Isatineeic acid c,OI-IlGOB, is a dihydroxy, diearboxylic acid and
the function of all its six oxygen atoms is therefore kno"·n.
Isati<line, c,SH25NO,, •tceorcling to Blad:ie (1907) may haYe three
r-eadiYe hydrogen atoms (i.e. hydroxyl-groups), aml the J·etttaining
four oxygen atoms must then be contained either in b\·o ester•
linknges or in one ester-linkage and one lactone g-roup.
Isatineeic acid so reaclily forms a monolactone (see experimental
part), that the slightest deviation from the optimum conditions for
the formation of the dibasic acid results in the isolation of the
monobasic monolactonic acid. 'l'he eqmdion for the h~·(lrolysis of
the alkaloid may therefore be either:
+ +
I. C1sH25N07 2 H20 = CsH1303N CJOH1606
isatidine isatinccinc if\atinecic acid or the
'new' acid (sec p. 445).
or
+ +
II. C1H 5N07 H 0 C H 0 N C\oHH05
8 2 2 8 13 3
isatidine isatinecine isa.tinecic monolactone.
HeYersely the alkaloid can therefore either be constituted by
the ('ombination of the diba.sic acid, C, H, .. 0 with the base
0 6,
isatinecine, C H, 0 N, by two ester-linkages, e.g·.
8 3 3 -l
( * HO
OH * * 3 react. H. atoms.
CsHloN ........... . ~ - * HO -- J~C 6H6.
1- 0
CO (CH
l- 0 co - 3)2
434
H. L. DE WAAL.
Or the alkaloid may be a combination by one ester-linhng of
isatinecine with the monolactonic acid as follows:-
tr -l
0
1- OH * I
oc - 1 * 3 react. H. atoms.
~·
C,H,N ............ OH * IC6H6.
* HO - (CH3)2
0 - co - J
C H N0 (isatidine)-sce equation II.
18 15 7
The Nat~t?'e of the Natural and Hyclro[Jenated lsatinecic Acids.
As is described. in the experimental part isatidine yields two
different acids on hydrolysis, depending upon the method used. vVith
alcoholic KOH a dibasic acid, U, H'"0 with melting-point
0 6,
181·0° C.':' and dextro-rotatory is obtained (see de \Vaal, 1939);
this acid as has now· been found also forms monobasic monohctonic
acid. Using Ba(OH) for the hydrolysis an isomeric dihy<hoxy
2
dibasic acid. is obtained, \Yith melting-point 148 ·5° C. and either
inactive or dextro-rotatory. Its corresponding monolactone has now
also been isolated for the first time with an [a J if = + 108 · 8(H 0)
2
and a melting-point of 197-8°C. In a private communication to the
author, Dr. J. J. Blackie of Edinburgh suggested the name
"isatineeic acid" to the Ba(OH) hydrolysis acid of m.p. 148·5° C.
2
which ''"e now will retain iu future, and the KOH-hy<lroly;;is aeid
of melting-point 181· 5° C. will meanwhile be termed the " ne\Y "
acid. until its identification ba.· been completed and a suitable name,
if necessary, suggested.
Both " isatinecic " acid and the " new " acid as well as their
monolactones (which incidentally prove that in each case one
hydroxyl-group must be situated in the y-position to one carboxyl
group) can be very readily hydrogenated in the presence of Pt0 In
2•
each case 2 molecules of hydrogen are consumed for one molecule of
the acid. As these hyrlrogenatecl acids persist to be of a syrupy
nature it is hoped that it will he possible to isolate ester-derivatives
in a crystalline form.
No"· octahydro-anhydro-isatidi ne, C H 0 N, on hydrolysis
18 31 6
yields a basic fraction C H 0 N, thus aceounting for t\YO moleeules
8 17 3
or four atoms of hydrogen. Again, octahydro-anhyclro-isatidine
sho\\-s a nett increase of six hydrogen atoms only and a loss of one
oxygen atom (although 8 atoms of hydrogen had been taken up
during the hydrogenation). Therefore the loss of two h~7drogen atoms
and one oxygen atom as one molec~tle of 1cnter must ha1.:e occvrred in
the acidic moiety of the hydrogenated suhstanre, C, H 0 N. I£ such
8 31 0
an intramolecular elimination of one molecule of water ha<l taken
place in the acidic fraction of the molecule, then it is expected that
the hydrolysis of ocbhyclro-anhydro-isatidine ''"ill lead to the isolation
of a C H 0 dibasic acid which had lost one molecule of water, i.e. a
10 20 0
C, H 0_, dibasic acirl. Should the hydrolysis lead to the isolation
0 18
of a monolactonic acid, then similarly its formula will be C, H 0
0 10 4
(i.e. C H, 0,-H 0).
10 8 2
--------------------------------------------------
* .·\II melting-points are corrected (Kotler micro-melting-point apparatus).
21 4;:35
THE SENECIO ALI{ALOIDS.
It is also perfectly clear from the two part formulae for isatidine
(see page 434) that the loss of one molecule of water in the acidific
moiety of the hydogenated substance cannot be due to a lactone
formation in that part of the molecule. It can only be accounted for
by the reaction o£ one hydroxyl-group _with one ?t~er hyd1:ogen atom
to eliminate one molecule o£ water m the aCidiC fract10n of the
molecule.
It is hoped that this obscure problem will be clarified in our
next contribution on the subject after the number of the reactive
H atoms in octahydro-anhydro-isatidine has been determined and
the hydrogenated acidic fraction has been isolated. Similarly it will
be interesting to know whether the same phenomenon of water elimi
nation takes place during the hydrogenation of isatinecic acid itself
as well as its monolactone.
ExPERIMENTAL PART.
Catalytic Hyd1·ogenat1:on and Red1tction af Isatidine and the
I solation of OctahyJ:ro-anhydro-isatidine.
10 Gms. Isatidine dissolved in 70 c.c. N hydrochloric acid was
hydrogenated under continuous mechanical shaking (Gattennann
and ,Wieland, 193G) using 200 mgm. platinum-dioxide as catalyst.
'l'he hydrogen consumption advanced as follows:-
The first molecule of hydrogen was taken up after 100 minutes,
i.e. at the Tate of 420 c:.c. Hz per hour.
The second moleeule of hyLhogen 11·as taken up a:Eter a further
110 minutes, i.e. 390 c.c. Hz per hour.
The third molecule o£ hydrogen was ta ke11 up after a furthe1·
145 minutes, i.e. at about 290 c.c. H per hour.
2
The fourth molecule of hydrogen was taken up after approxi
mately 250 minutes, i.e. at about 170 c.c. per hour.
Various independent hydrogenations with 3 gms., 12 gms. ann
20 gms. of isatidine and 100 mgm., 200 mgm. and 500 mgm.
platinum-dioxide respectiYely in w::tter, half-normal and normal
h:vdrochloric a!'icl solutions all proved that the first two molecules
of hydrogenation were absorbed at practically the same rate but that
the consumption of the third molecule of hydrogen \Yas much slower,
whereas the fourth molecule of hydrogen was consumed at a still
more reduced rate.
'fhe hydrogenated acid solution (above) of 10 gms. of isatidine
11·as very unstable to\\·ards acid or soda-alkaline pennang::mate solu
tions and gave strong precipitates with Mayer's, Wagner's and
Dragendorf's reagents and with phospho-tungstic acid. Thorough
shakings of this acid solution with ether or with chloroform removed
nothing. 'l'he solution was then alkalinified with concentrated
ammonium hydroxide (1 : 3H 0), allowed to evaporate and finally
2
dried in a vacuous olesiccator over concentrated sulphuric acid. The
residue was then extracted first with acetone (twice) and then with
chloroform followed by absolute alcohol.
436
11. L. DE \\"AAJ ..
The acetone solutiorr deposited a good c:rop of crystals (about
:2 gms.) ~wd the chlorofOl'm solution on cYaporation left about 5 gms.
of an oiJ_v substauce.
The pm·if-ied n yst;1];; (sec l<'ig. 1) from the ac:eloue solution \l·as
dissohed in a little ahc:olute al(·olwl from which it c:rysblli~~,ed in
cluste1'S of nec<lles on tl1e addition of a small Yolume of d rv ether.
l<'1·om thr oih· residue of tlw ('hloroform extract the s;~me :-;;Ihstan<·e
or
was isola!ed ·,d.ter repe::llcd he:1bncnt the oil with acetone. The
;t('etoue 11·ashing'S deposited !he s<~me l>ase as 11·;u-; isolated above.
This base exhibited a double mcliir1g point. lt melted nt 115 to
120°, J'<•solidified :llld final\.1· mcHt·<l to a l'll·ar :.;olution a! 181 (o
18 -~0 (;_
HrG. 1.
Oc;ta-ilydro-n n ilyclro-isa tidi llC x 3-5.
,1/ lcro-onalys£s.
0 -:3-1-i mgm. : ll<)(j,) mgm_ C02 ; -1-·] 10 mgm. IT 2U.
:{- \-1--1- mgm.: O·J0-1- c.c. ::'\ :1t .22·!">° C. an(l 7GG m.m.
C'alr-11lall'd for C H" 0r.::'\:
18 1
C= GO--:l-i-i p<'r c:ent.; l-I=~)·i-1- per cent.; N = ;l-92 per cent.
found:
C= 59-01 Jler ec11t.; l-I= 8·73 prr ('Cilt.; N = ;l-85 per cent.
(SP(' r·onfi rm:d ion of this fonnu b from tlH· :111:ilysis of its hyrlro
chloride, p. 439).
'1'\w subsbwce hall :1 hitler L1ste; it n~aclily rlissoh·e<l in waLL'r,
llll'thanol arHl acclil' al'i<l: it 11·aq solul1le in ethanol an(l chloroform;
it was sparing-ly soluble in fl('e(one, ben;,ol an(l rth~-1-al'dnte and
437
THE SE::\EClO ,\Ll\ALOlDS.
"·a,; insoluble in ether and petroleum-ether. A .-;ulutiou of octahydro
anhydro-isatidine iu twice-normal hydrochloric acid gave strong
precipitates with phospho-tungstic a<·id and with l\Iayer's, \Vag-ner':-;
and Dragendorf"s alkaloidal reagents.
The formula cl8H3,0GX wa.-; definitely established by the prepa
ration of the hydrochloride from this base and the isolation of the
hychoc:hloride hom the hydrogenated acid solution.
J solation of Octah.ydro-a1111 ydro-isatid in e-hydroch lor ide.
This <'Om pound ''"a" Yery n·<1cli 1~- obtained \dtPn isalicline "·as
<·uta Jyh cally reduced in <I normal hyclroehlorie acid solution (see
aboYe) nn<l the filtrate nftpr !he hy<lrogenation allo"·ed lo eYaporate
in front of a fnn at rdOJll t<'mpnatun'. C'n·stuls rapi<lly bcg·an to
;;eparutl' in the fontl of stout prismatic l"Olum11s. ThP liquid was
finally CYaporated to <lryne~s on a "·;J(er-bath. The n yslals '"ere
dried, washed with acetone follo"·ecl b.Y ether <UHl recrystallized from
hailing- ethanol. After t"·o n'cr:ysblliY-ations tlw hychochlori<le (see
.Fig. 2) meltecl sharply nt 218° ,,·ith strong eYolution of g-as to n
l"leflr melt. ·
Octa-1'-'·dro-an !J_,·d ro-isat tel i ne-hyd roch Iori de x 3,3_
Optical Rotation.
\\.ht ....... . 50·0 mgm.
\'ol ......... . 7 · 5 c.c. H 0.
2
8 .......... . - 0·35.
- 0·3.') X 7·5 X 1,000
1 X 50
438
H. J,. DE WAAL .
.I I ino-uuulys1s:
5·107 mgm.: 10·875 mgm. C0 3·870 mgm. H 0.
2: 2
2 · 914 mgm. : 0 ·090 c.c. N at 23°C and 766 nun. Hg.
13·420 mgm.: 4·940 mgm. AgGI.
Calculated for C H 0 N.HCl C. = 54· 88 per cent. : H = 8 · l 9 per cent.
18 31 6
N = 3 ·55 per cent. : Cl = 9 ·00 per cent.
Found.. .. . .. .. .. .. . .. .. . .. .. C. = 54· 87 per cent. : I-I = 8 · Ol per cent.
N. = 3 ·59 per cent. : Cl = 9 ·10 per cent.
Therefore. . . . . . . . . . . . . . . . . . . . C H 0 N.NC1.
18 31 6
The substance was readily soluble in 11·ater, methanol and acetic
acid; it was sparingly soluble in ethanol, ethyl-acetate and chloroform
and it was insoluble in ether, acetone and petroleum ether.
PrezJamtion of OctahydTo-anhydro-isatidine (free base) j?·om the
above hydrochloride.
'l'he pure hydrochloride (m.p.218°) was dissolved in a small
volume of water and the solution made alkaline with a concentrated
ammonium hydrate solution (1:3 H 0). It "·as then allowed to
2
evaporate in front of a fan. The residue, which had the consistency
of a syrup, was stirred with dry acetone when it became crystalline.
Purification was effected by recrystallization from ethanol on the
addition of a small volume of pure ether. The base had the same
double melting-point and showed no depression when mixed with the
free base directly isolated from the isatidine-hydrogenated solution
(see page 43G).
Hydrolysis of Octahydro-anhyd1·o-isatidine and the 1 solation of
Tetrahydro-isatinecine.
'l'he hydrolysis of Octahydro-anhydro-isatidine can be effected
in t\VO ways: (1) immediately after the hydrogenation (Pt0 of
2)
isaticline was completed, i.e., with the base still in normal hydro
chloric acid solution, or (2) with the crystalline hydrochloride after
its isolation. In the first case the filtrate, after 4 molecules of H
2
had been taken up by the isatidine in N-HCl solution, was shaken
with ether. 'fhe ether was removed and the acid solution neutralized
with concentrated ammonium hydrate (1: 3 H 0) and then 1· 2 mol.
2
of solicl barium hydrate were added. In the second casf' the (·rystalline
tetrahydro-anhyc1ro-isatic1ine hydrochloride was dissolved in a small
volume of water and a small excess of barium oxide-hydrate \Yas then
added.
The solution (in either rase)with the barium hydrate was then
re:fluxed for about one hour [e.g., 10 gms. octahydro-anhydro
isatidine and12 gms. of Ba(OH) ·8H 0 ]. It was then filtered. The
2 2
filtrate was titrated with concentrated sulphuric acid (l :4 H 0) until
2
just acid to phenolphthalein. The BaSO,, was centrifuged off. The
clear supernatant was allo'll·ed to evaporate on a ·waterbath to dryness
and the dry residue extracted with hot absolute alcohol. The alcoholic
solution was then allowed to evaporate on a waterbath and the syrupy
residue stirred with dry acetone. The base crystallized.
439
THE SEKECIO ALrUJ,OlllS.
'l'his substance was then Tepeatedly refluxed with acetone which
removed the base and on the concentration of the acetone and the
additioli of a small volume of e( her readily crystallized (see Fig. 3).
After one or two similar recryRtalliza tions this base tetrahydro
isatinecine, had a constant melting-point (sharp) of 174·5°. It is
ve1-y hygroscopic.
FrG. 3.
Tehnh.Ydro-isatinc<.;ine, Jll.p. 175xl0.
Micro-analysis:
5·201 mgm.: 10·380 mgm.C0 4·440 mgm. H 0.
2 ; 2
3·021 mgm.: 0·210 c.c.N at 25·5° C. and 754 m.m. Hg·.
Calculated for C H 0 N :
8 17 3
C= 54·83 per cent.; H = 9·78 per cent.; N = 7·99 per cent.
found:
C= 54·43 per cent.; H = 9·55 per cent.; N = 7·90 per cent.
Optical 1·otation .
The mean value of a solution of 50· 0 mgm. in 8 · 0 c.c. distilled
H 0 was found to be as follows : -
2
a= - 0·55°.
J
Therefore [ a ~O = - 88·0°.
Chemical Properties :
This substance (tetrahydro-isatinecine) was easily soluble in cold
water, ethanol, methanol and chloroform.
It readily dissolved in hot acetone; it was sparingly .solul,le jn
ethyl-acetate and practically insoluble in ether and petroleum-ethel.
A solution of tetrahydro-isahnecine in t\vo normal HCl gave
strong· precipitates with phosphotungstic acid and with Wagner's,
-+4 ()
H. L. DE II".AAL.
Dragendori's and .Mayer's reagents. With :Mayer's reagent lemon
yellow crystalline flakes were obtained with a cruue melting-pomt
o:£ 117°. 'l'etrabydro-isatinecine was unstable towards soda-alkaline
potassium-pennanga.nate solution.
Bm·ium,-hydroo?:ide hydrolosis of Lsatidine. '' The 1·solation of ...
isatinecine, isatinecic acid and isatinecic monolactonic acid.
To a solution of 20 gms. of isatidine in 200 c.c. of water was
added 20 gms. of solid barium-oxide-hydrate (1·2 mol.) and was then
refl.uxed for 40 minutes. 'l'he filtrate "·as titrated with concentrated
sulphuric acid (1:4 H 0) until just :1cid to phenolphthalein and the
2
BaS0 precipitate centrifuged off. 'l'he supernatant was decanted
4
and evaporated on a water bath under reduced pressure. The dry
residue "·as then twice extracted with hot ethanol which readily
removed the base isatinecine.
On concentration of the alcohol and the addition of acetone
isatinecine crystallized out in a very good yield of about 8 gms.
Thus recrystallized the basic fission product (see Fig. 4) decomposed
at 212-215°.
FIG. 4.
lsatinecine, m.p. 212-5°, XlO.
.1 1i c1·o-auolysis.
4 · 729 mgn1. dried at room temperature in high vacuum over
P 0 lost 0 · 058 mgm. in weight.
2 5
(a) 4 · 671 mgm.: 9 · 655 mgm. C0 3 ·160 mgm. H 0 .
2 ; 2
• Ln a private communi<:ation Dr. J. J. Blnckie of Edinburgh suggested the
ilydroi~·,is 11·ith Ba(OH), for which 1re w1sh to express our si.ncere thanks .
..J.-1 L
THE SENECIO ALI{AJ,OIDS.
(b) 2·865 mgm.: 0·214 c.c. N at 25° C. and 764 m.m. Hg.
found: C= 56·41 per cent.; H = 7·57 per cent.; N=8·6
per cent.
Calculated for C H, 0 N: C=56·12 per cent.; H = 7·65
8 3 3
per cent.; N = 8 · 2 per cent.
(c) Active hydrogen could not be determined due to the insolu
bility of the substance in either pyridine or anisole.
(d) Negative for C-methy l groups.
(e) Negative for N-methyl groups.
Optical Rotation.
[a]
2DO = +22·4° (50·0 mgm. w 8 c.e. H 0J
2
Properties.
h ::rtinecine gave :;hong precipitates with phosphotungstic acid,
Wagner's and Dragenrlorf's reagents, but nil "·ith Mayer's reagent.
It iR soluble in water, methanol, ethanol and acetic acid.
It is sparingly soluble in acetone and ethyl-acetone mul practi
cally insoluble i11 ether, petroleum-ether and chloroform.
isolation of I satinecic Acid and lscd1:necic M onolacton-ic Acid.
The residue after the extraction of the base with ethanol (above)
was then dissolverl in a small volume of \Yater, titrated with concen
trated sulphuric acid (1 : 4H 0) until the solution was this time just
2
acid to congo red. The BaSO,, was again centrifuged off :mel the
SUJlernatant evaporated to dryness as already stated for the base
above. The dry resiclue "·as thE'n refluxed with ethyl-acetate fm two
to three minutes which removed the acid, the ethyl-acetate solution
was dried over exsic(:ated N a SO_, and if necessary decolourised by
2
the addition of a pinch of charcoal. On the addition o£ a little petro·
leum-ether to the filtrate isatinecic acid crystallized in needles. After
a similar recrystallization the acid crystallized in fairly large
beautiful colourless needles (see Fig. 5) with a clear constant melting
point of 148 ·5°.
When similar hydrolysis experiments of isatidine "·ith barium
hydroxide were carried out under slightly excessive heat, the hyclro
lysis invariably resulted in the isolation of the isatinecic monobctonic
acid. This monolactonic monobasic acid readil.v crystallizes into
beautiful brge crystals (see Fig. 6) from pure ethyl-acetate only.
After the third recrystallization the substance was pure with a sharp
melting-point at 197-8° C.
442