close

Вход

Забыли?

вход по аккаунту

?

Preparation of -Methyl 2 3-O O-Isopropylidene-4 6-dideoxymannopyranosid-4-ene.

код для вставкиСкачать
salts (1)-(3) are rapidly decomposed by moisture, but (4)
can be kept open to the air for several hours since its orthomethyl groups shield the center of the positive charge.
The proton magnetic resonance spectra [4] of (3) and (4) in
dichloromethane with tetramethylsilane as internal standard
contain the following signals on the &scale: (3), -9.68
(proton on the carbonium carbon), -7.84, -7.69, and -7.33
(benzene ring protons), -7.17 (mesitylene ring protons), and
-2.58 (methyl protons); ( 4 ) . -9.69 (proton on the carbonium
carbon), -7.15 (mesitylene ring protons), and -2.50 and
-2.43 (methyl protons; relative intensity = 1:2). The methyl
proton signals of (4) remain unchanged between -60 and
f 9 0 “C.
The infrared spectra of (I)-(4) in Nujol, Kel-F, or hexachlorobutadiene indicate a strong activation of the C = C
vibrations, a reduction in the intensity and shift to higher
frequencies in the y-vibrational region, and a broad and very
intense band in the CsBr range at 339 cm-1 due to the
asymmetric stretching vibrations of the SbCIbe ion.
The strengths of the carbonium ions as acceptors for chloride
ions were determined by reaction with the corresponding diand triarylmethyl chlorides in carbon tetrachloride and
chloroform and measurement of the yields of products. These
increasealong the series triphenylmethylQ<(4)<(I),(2)<(3).
An equilibrium is attained in the reaction of ( 4 ) with triphenylchloromethane in chloroform which lies to 66-69 %
on the side of triphenylmethyl hexachloroantimonate.
The salt ( I ) reacts with ethyl triphenylmethyl ether to yield
benzhydryl ethyl ether. The reaction of ( I ) with water or 2 N
sodium hydroxide gives mainly dibenzhydryl ether plus some
benzhydryl chloride (from internal return of the chloride
ion), benzophenone, and diphenylmethane (from hydride
transfer between ( I ) and benzhydrol). If the salts are suspended in benzene and shaken with water or 2 N NaOH,
( I ) and (3) give diarylchloromethanes as main product
together with some bisdiarylmethyl ether by reaction at the
interface, but (4) yields exclusively dimesitylmethanol.
Aromatic compounds R-C&
are alkylated by ( I ) at room
temperature by a Friedel-Crafts reaction para to the substituent R; the yields are: R=H, 22-29%, R=CH3,40-42 %,
and R=OCH3, 61-65%. The reaction of ( I ) with benzhydro1 in benzene gives 93 % triphenylmethane, 6 % cr,a,c(’,a’tetraphenyl-p-xylene, benzophenone, and diphenylmethane.
The reaction of the salts with methanol or ethanol produces
alkyl diphenylmethyl ethers.
Received: July 22nd, 1965
[Z 38/869 IEI
German version: Angew. Chem. 77, 864 (1965)
[l] Stable Carbonium Ions, Part 5 . Part 4: H. Volz, Tetrahedron
Letters 1964, 1899.
[2] H. Volz, Angew. Chem. 75, 921 (1963); Angew. Chem. internat. Edit. 2, 622 (1963).
[31 H. J . Dauben, L. R . Honnen, and K . U. Harmon, J. org.
Chemistry 25, 1442 (1960).
[4] The spectra were kindly recorded by Dr. H . A . Brune.
it is rather unstable. Reduction with LiAIH4 in ether for
30 min at room temperature gave a mobile oil which contained no sulfur or free hydroxyl groups. The excess LiAIH4
was decomposed with water and the product extracted
with chloroform. The extract was washed with water and
dried over sodium sulfate, and the chloroform was evaporated off on a water-bath. The residual oil was taken
up in low-boiling petroleum ether and the solution washed
with water and dried. The solvent was evaporated off and the
residue vacuum distilled (b.p. 93-96’C/13 mm; [a]&: =
-193O, c = 1 in chloroform). The composition and NMR
spectrum of the product indicate it to have the structure (2).
H
The NMR signals for (2) at 60 Mc/s in CC14with tetramethylsilane as internal standard are: isopropylidene protons T =
9.10 ppm (3 H) and 9.02 (3 H); C-6 protons, T = 8.63 (3 H);
C-2 proton, 6.58 (triplet, 1 H); C-3 proton, 6.01 (approximated triplet, 1 H), C-1 proton, 5.90 (doublet, 1 H); C-4
proton, 5.70 (doublet, 1 H) OCH3 protons, 6.93 (3 H). The
~ 5.5 c.P.s., 52.3 = 5.5 c.P.s., J3,4 =
coupling constants are J I , =
4 c.P.s., 54.6 = 1 c.P.s., and 53.6 = 1 C.P.S.
Received: July ZZnd, 1965
[Z 35/861 IE]
German version: Angew. Chem. 77, 863 (1965)
[ I ] J. Lehmann and A . A . Benson, J. Amer. chem. SOC. 86, 4469
(1964).
Synthesis of a-Methyl [5-3H]-~-Glucosideand
@-Methyl[5-3H]-~-Idosideby Hydroboration of
Substituted Methyl Glucosidenes
By Dr. J. Lehmann
Chemisches Institut
der Universitat Freiburg (Germany)
The trimethyl ether ( I ) and tristrimethylsilyl ether (2) of crmethyl D-glucopyranosid-5-ene[l] can be hydroborated by
passing diborane into their solutions in tetrahydrofuran. This
method can be used to achieve specific labelling of sugars
with tritium or deuterium.
The reaction of ( 1 ) and (2) with [SHIdiborane [2] and
subsequent removal of the protective groups lead respectively
to 1:2 and 1:0.6 mixtures of cr-methyl [5-3H]-~-glucoside( 3 )
and P-methyl [5-3H]-~-idoside(4).
cHZ
Preparation of a-Methyl2,3-0,0’-Isopropylidene4,6-dideoxymannopyranosid-4-ene
By Dr. J. Lehmann
Chemisches Laboratorium
der Universitat Freiburg (Germany)
=-Methyl 6-deoxy-2,3-0,0‘-isopropylidenemannopyranosid5-ene [ l ] in pyridine was cooled in ice and treated with
methanesulfonyl chloride to form the 4-0-methanesulfonyl
ester ( I ) . The reaction mixture was stirred Into a saturated
solution of NaHC03 at 0 OC, and the resultant solution was
extracted with chloroform. The organic phase was dried
with N a ~ S 0 4and the chloroform distilled off. The sirupy
residue of ( I ) obtained was processed immediately because
874
H (2)
OR
.c
CHzOH
For example, (2) is hydroborated for 2 h at ca. 20 OC and the
excess diborane is decomposed with methanol. The solution
is evaporated in vacuum to a sirup, which is mixed with
Angew. Chem. internat. Edit./ Vol. 4(1965) 1 No. 10
Документ
Категория
Без категории
Просмотров
4
Размер файла
129 Кб
Теги
preparation, methyl, ene, dideoxymannopyranosid, isopropyliden
1/--страниц
Пожаловаться на содержимое документа