Monomesylates

CN 4-[[4-[(aminoiminomethyl)amino]benzoyl]oxy]benzeneacetic acid 2-(dimethylamino)-2-oxoethyl ester monomesylate... 

CN (5 a, 10a)-9,10-dihydro-12 -hydroxy-2 -( 1 -methyIethyl)-5-(phenylmethyl)crgotaman-3, 6, 18-trione monomesylate... 

The key cyclization in Step B-2 was followed by a sequence of steps that effected a ring expansion via a carbene addition and cyclopropyl halide solvolysis. The products of Steps E and F are interesting in that the tricyclic structures are largely converted to tetracyclic derivatives by intramolecular aldol reactions. The extraneous bond was broken in Step G. First a diol was formed by NaBH4 reduction and this was converted via the lithium alkoxide to a monomesylate. The resulting (3-hydroxy mesylate is capable of a concerted fragmentation, which occurred on treatment with potassium f-butoxide. 

Cyclobutanecarbonyl chloride, reaction with erythro-2,3-butanediol monomesylate, 51, 12... 

BUTANAL, l-d—2-METHYL-, 51, 31 erythro-2,3-Butanediol monomesylate, by reaction of trans-2-butene oxide with methanesulfonic acid, 51, 11 3,5,1,7-[1,2,3,4]Butanetetrayl-naphthalene, decahydro-, 53, 30... 

CYCLOBUTANE, l-BROMO-3-CHLORO-, 51,106 Cyclobutanecarbonyl chloride, reaction with erythro- 2,3-butane-diol monomesylate, 51,12 CYCLOBUTANECARBOXALDE-HYDE, 51,11... 

Similarly a diol 1 with given relative and absolute configuration may be monomesylated to give 2 and 4 which are cyclized with base to the epoxides 3 and 5. 

This sequence demonstrates that although the stereochemistry is unambiguous in each step, regiochemical uncertainty eventually leads to the loss of the original stereochemical information. Hence, it is essential to control the regiochemistry of both monomesylation (or tosylation) and epoxide opening. 

This line of thinking prompted the treatment of 86 with zinc in refluxing methanol for the purpose of generating 88. When this ketone was reduced with diisobutylaluminum hydride in tetrahydrofuran at low temperature, the cis diol 89 was produced with a stereoelectivity in excess of 10 1. Monomesylation of the... 

Once 94 was in hand, it proved an easy matter to bring about its transformation regioselectively into the monomesylate and to bring about subsequent Grob fragmentation. These two steps delivered 95 with a level of efficiency (85% overall) higher than that previously encountered in the all-cis series, viz. 63 66. 

Further hydrolysis of the compound 55 with 7% HCl-MeOH followed by treatment with MsCl-pyridine and then with LiCl in dimethyl-formamide (DMF) (90-100°, 18 hr) afforded a monomesylate [56, mp 253-254° (as hydrochloride)] via deacetyldeoxyyuzurimine (57) and dimesylate (58). In the NMR spectrum of 56, a broad singlet resulting from two olefinic protons was observed at 5.93. Finally, catalytic hydrogenation of this compound over Pt02 gave yuzurimine-B mesylate (54) which was directly obtained from yuzurimine-B on mesylation with MsCl-pyridine. 

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