Pentaacetyl derivative

The aminocyclitol d-48 was synthesized from l-218 (Scheme 28).103 Since direct peroxyacid oxidation of the exo-methylene group of compound l-218 had been shown to give selectively the undesired /<-spiro epoxide,35 102 it was first converted into l-219, followed by oxidation with m-CPBA to give the desired x-spiro epoxide d-220 (80%). The alcohol d-221 obtained in 73% yield by reductive cleavage of epoxide d-220 with lithium triethylborohydride (LiBHEt3) in THF was formed as a 2 3 mixture of two alcohols. However, hydrolysis of d-221 with hydrochloric acid gave d-48 (94%), which was further characterized by conversion into the pentaacetyl derivative 222 (82%). 

From the mother liquors of the crystallization of spectinomycin was isolated a compound that was identified as dihydrospectinomycin80 (see Scheme 21). The n.m.r. spectrum of the pentaacetyl derivative... 

Degradation of dihydrostreptomycin in methanolic hydrogen chloride yielded methyl dihydrostreptobiosaminide, which formed a pentaacetyl derivative on acetylation. - - - Both anomers of this compound were isolated.The crystalline methyl pentaacetyldihydrostreptobio-saminfde was also obtained by selective hydrolysis of the non-glycosidic acetal group in methyl streptobiosaminide dimethyl acetal followed by catalytic hydrogenation and acetylation. 

Wolfrom and coworkers had found that the mercaptolysis of the crystalline calcium chloride double salt of streptomycin trihydrochloride yielded, after chromatographic purification, two anomeric forms of ethyl tetraacetylthiostreptobiosaminide diethyl mercaptal. Mercaptolysis of dihydrostreptomycin yielded an amorphous ethyl dihydrothio-streptobiosaminide hydrochloride which formed crystalline N-acetyl and pentaacetyl derivatives. The ability of the ring in this latter compound to resist hydrolysis and to form a thioglycoside instead of a thio-... 

Hydrolysis with aqueous mercuric chloride in the presence of cadmium carbonate removed the thioethoxy groups in ethyl tetraacetyl-thiostreptobiosaminide diethyl mercaptal. Crystalline tetraacetylstrep-tobiosamine was obtained in this manner. Bromine oxidation of tetraacetylstreptobiosamine in the presence of strontium carbonate yielded an acid which, after reacetylation, was obtained as the crystalline pentaacetyl derivative. The analytical data and the results of potentio-metric titrations for this oxidation product, designated pentaacetyl-streptobiosamic acid monolactone, were in agreement with the formula, Ci3Hi6NOio(CH3CO)5, required for a dibasic acid monolactone. A crystalline monomethyl ester of the substance was prepared. The established formula shows that all hydroxyl groups present are acetylated or lactonized. 

Unlike the other streptobiosamine derivatives (Table IV, page 383) streptobiosamic acid monolactone formed a pentaacetyl derivative " rather than a tetraacetyl compound. Also, acetylation of streptosonic acid monolactone yielded a diacetyl derivative. It was pointed out that either the ordinarily resistant tertiary hydroxyl group had been acetylated in these compounds (XXVII) or that the lactone ring had shifted from the 7- to the /3-position, during the acetylation, with the introduction of an acetyl group at carbon atom four (XXVIII). Whatever the positions of the ester groupings in pentaacetylstreptobiosamic... 

Problem 34.22 (-f-)-Glucose reacts with acetic anhydride to give two isomeric pentaacetyl derivatives neither of which reduces Fehling s or Tollens reagent. Account for these facts. 

In the deprotection of peracetylated polyphenolic compounds a somewhat different scheme has emerged. In this area, a broader spectrum of lipases has been used successfully. For example, the pentaacetyl derivative of catechine 179 was treated with PSL under alcoholysis conditions (THF, n-butanol) to give the 3,3, 4 -trisacetate in 50% yield after 12 hours12781. On longer exposure to the biocatalyst, the 3-monoacetyl derivative was isolated in 95 % yield. 

A 4 Rrom(jb[Pg.129]

Base A, C29N37O13N (mp 260° [a]n -I- 21), contains five acetyl groups and can be converted to a pentaacetyl derivative which is alkaloid C. 

---