Aqueous methanol

Boil the crude coumarin with 200 ml. of water to which 0 -2 g. of decolourising carbon is added, filter the hot solution, and concentrate it to a volume of 80 ml. Cool, collect the coumarin which separates, and recrystallise it from 40 per cent, aqueous methanol. The yield of coumarin, m.p. 68-69°, is 1 0 g. 

When the reaction was earned out m aqueous methanol as the solvent hexyl bromide was converted to hexyl cyanide m 71% yield by heating with sodium cyanide Although this IS a perfectly acceptable synthetic reaction a peiiod of ovei 20 hours was lequued Changing the solvent to dimethyl sulfoxide brought about an increase m the reaction rate... 

Another example is the purification of a P-lactam antibiotic, where process-scale reversed-phase separations began to be used around 1983 when suitable, high pressure process-scale equipment became available. A reversed-phase microparticulate (55—105 p.m particle size) C g siUca column, with a mobile phase of aqueous methanol having 0.1 Af ammonium phosphate at pH 5.3, was able to fractionate out impurities not readily removed by hquid—hquid extraction (37). Optimization of the separation resulted in recovery of product at 93% purity and 95% yield. This type of separation differs markedly from protein purification in feed concentration ( i 50 200 g/L for cefonicid vs 1 to 10 g/L for protein), molecular weight of impurities (<5000 compared to 10,000—100,000 for proteins), and throughputs ( i l-2 mg/(g stationary phasemin) compared to 0.01—0.1 mg/(gmin) for proteins). 

Arabinan. This highly soluble polymer is found in the extracts of many fmits and seeds, in the boiling water extracts of pine wood (127), in the extracts of marshmallow roots (A/t/jaea officina/is) (128), and aspen (63) and willow (Sa/ix a/ba F) (129) bark. Because arabinan can be isolated from mildly degraded pectin fractions, it is often difficult to determine whether it is a hemiceUulose or a labile fragment of a larger polysaccharide and/or lignin complex. Arabinans have a complex stmcture composed almost entirely of 5-linked a-L-arabinofuranosyl units with similar residues linked to them at C-2 and/or C-3 and is soluble in 70% aqueous methanol solution. 

EthynodlolDia.ceta.te, Ethynodiol diacetate has been used alone, and in combination with an strogen, as an oral contraceptive and to treat disorders associated with progesterone deficiency (76). It may be crystallised from aqueous methanol (77) and is soluble in chloroform, ether, and ethanol sparingly soluble in fixed oils and insoluble in water (76). Extensive spectral and chromatographic data have been compiled (78). 

Megestrol acetate can be recrystakhed from aqueous methanol (108). It is soluble in acetone, chloroform, and ethanol slightly soluble in ether and fixed oils and insoluble in water (107). Additional spectral and physical data have been pubHshed (62). 

An example of an alkyl monoperoxycarbonic acid, 0-ben2yl monoperoxycarbonic acid [52123-51 -0] was prepared ia aqueous methanol solution by basic perhydrolysis of diben2yl peroxydicarbonate [2144-45-8] and subsequendy isolated ia 97% purity. It has been used as an epoxidi2iag agent (185) ... 

In the piepaiation of ioveisol (12) (41), the key intermediate (23) is prepared from the diacid (20) by the action of thionyl chloride followed by 3-amino-l,2-propanediol. The alcohol groups of (23) are protected as the acetates (25), which is then N-acylated with acetoxyacetyl chloride and deprotected in aqueous methanol with sodium hydroxide to yield (26). N-alkylation of (26) produces ioversol (12). 

Me3SiNEt2- Trimethylsilyldiethylamine selectively silylates equatorial hydroxyl groups in quantitative yield (4-10 h, 25°). The report indicated no reaction at axial hydroxyl groups. In the prostaglandin series the order of reactivity of trimethylsilyldiethylamine is Cii > Ci5 C9 (no reaction). These trimethylsilyl ethers are readily hydrolyzed in aqueous methanol containing a trace of acetic acid. The reagent is also useful for the silylation of amino-acids. ... 

Aryl and alkyl trimethylsilyl ethers can often be cleaved by refluxing in aqueous methanol, an advantage for acid- or base-sensitive substrates. The ethers are stable... 

Dihydrocodeine [125-28-0] M 301.4, m 112-113°, b 248/14mm . Crystd from aqueous methanol. 

II, 20-dione to the corresponding tetrol has been given as 43 hours at room temperature in aqueous methanol. ... 

A solution of 2 g of sodium borohydride in 5 ml of water is added at room temperature to a solution of 1 g of 3a-hydroxy-5jS-pregnane-l 1,20-dione in 15 ml of methanol. Almost immediately, crystals begin to form. After the mixture has been kept overnight, the precipitate is collected with suction to yield 0.8 g of the diol, mp 230-232°. The analytical sample, crystallized once more from aqueous methanol, melts at 231.4-232.6° [a]p 31.2° (acetone). Reported mp 236-238°. 

When 3a,17a-dihydroxy-5jS-pregnane-ll,20-dione is allowed to react at room temperature overnight with sodium borohydride in aqueous methanol, no crystals form and only 5j5-pregnane-3a,l ljS,17a,20j5-tetrol is isolated in good yield. If the reaction is halted at the end of 3 h y the addition of water and extraction with chloroform, it is possible xo obtain a 55% yield of 3a,17a,20jS-trihydroxy-5j5-pregnan-ll-one, mp 218-220°,after recrystallization of the chloroform residue from aqueous methanol. The analytical sample, crystallized once more, has mp 219.0-220.6° [a][, 36° (acetone), reported mp 220° [aJu 38°. 

Oxidation of 20-keto-21-hydroxy steroids with oxygen in aqueous methanol or in anhydrous methanol in the presence of cupric acetate has been reported to give good yields of the corresponding 21-aldehydes. 

Hydrolysis of the ketal group with hot acetic acid or dilute aqueous methanolic sulfuric acid affords the 5a-hydroxy-6 -methyI-3-ketone (8). 

In a special case involving a C-ring aza steroid, it was found that epoxida-tion of a A -20-keto grouping using a two-phase system (t-butyl alcohol-aqueous potassium hydroxide-30 % hydrogen peroxide) was much superior to the standard hydrogen peroxide-aqueous methanolic alkali conditions. 

A solution of mercuric chloride (1.63 g) in ethanol (10 ml) and 38 % hydrochloric acid (1 ml) is added to a solution of the diene (2 g) in ethanol (20 ml) and water (1 ml), and the mixture is heated on the steam bath for 30 min. The ethylthiomercurichloride is filtered, washed with ethanol (5 ml) and dried, yield 96%. The filtrate is poured into water (150 ml) and the solid filtered, washed with water and crystallized from aqueous methanol, 4 1. After three crystallizations 41 % of 3, 21-dihydroxypregn-5-en-20-one is obtained mp 160-165° [a] 7° (CHCI3). 

Treatment of dibromocarbene adduct (43) (Rji, = O) with aqueous methanol containing silver nitrate or perchlorate gives A-homo-estra-1 (10), 2,4a-triene-4,17-dione (45) in 21 % overall yield from the enol ether (42). The exact pathway is not known, but the first step may be formation of a bromo-homo-dienone facilitated by the methoxyl group, which then undergoes further loss of hydrogen bromide involving shift of a double bond by enolization. ... 

Aryl and alkyl trimethylsilyl ethers can often be cleaved by refluxing in aqueous methanol, an advantage for acid- or base-sensitive substrates. The ethers are stable to Grignard and Wittig reactions and to reduction with lithium aluminum hydride at —15°. Aryl -butyldimethylsilyl ethers and other sterically more demanding silyl ethers require acid- or fluoride ion-catalyzed hydrolysis for removal. Increased steric bulk also improves their stability to a much harsher set of conditions. An excellent review of the selective deprotection of alkyl silyl ethers and aryl silyl ethers has been published. ... 

Thiohydantoin 9 was obtained from the treatment of carbonyl 1 with carbon disulfide and ammonium cyanide in aqueous methanol. The transformation could also be carried out step-wise, that is, treatment of 1 with ammonium cyanide to form aminonitrile 10 followed by reaction with carbon disulfide to produce thiohydantoin 9. Alternatively, 5,5-disubstituted 4-thiohydantoins could be prepared by the reaction of ketones with ammonium monothiocarbamate and sodium cyanide. ... 

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