Validamines synthesis

Novel Synthesis of Natural Pseudo-aminosugars, (+)-Valienamine and (+)-Validamine... 

Now, both the utility and the versatility of our method are demonstrated in the stereoselective synthesis of natural (+)-valienamine (25) and (+)-validamine (29) (7/) (Scheme 3). Furthermore, the anchor effect of an amino group will be described in the stereoselective hydrogenation of the olefin of25 to give 29 (Fig. 1). 

In summary, the novel synthesis of (+)-valienamine and (+)-validamine has been accomplished by our synthetic strategies for the constructing of carbasugars. The absolutely stereoselective hydrogenation of 26 and 27 to give (+)-validamine (29) is particularly noteworthy. 

The majority of naturally occurring aminocarbasugars bears the amino functionality located at the pseudoanomeric position however, replacement of one or more hydroxyl groups by amino functions on the carbasugar backbone may offer great opportunities for structural and stereochemical variation. This section is subdivided into three subsections, dealing with the synthesis of validamine, valiolamine, and valienamine-type carbaglycosyl amine structures. 

A nice stereoselective synthesis of validamine 202 was accomplished by Yoshikawa s group [51], capitalizing on the longstanding familiarity with cyclization of nitrofuranose derivatives [52]. The focal intermediate of the synthesis was nitrofuranose adduct 206 (Scheme 34), which was obtained via a high-yielding multistep transformation of D-glucuronolactone 205. 

Acefia, J.L. et al. A Stereodivergent Access to Naturally Occurring Aminocarbasugars from (Phenylsulfonyl)-7-oxabicy-clo[2.2.1]heptane Derivatives. Total Synthesis of Penta-N.O-acetyl-(i-)-validamine and Its Ci and C2 Stereoisomers. 3.4.1 1994 [101]... 

As shown in O Scheme 44, this method was also applied to total synthesis of (-i-)-valienamine (320) and (+)-validamine (324) [209]. Silyl enol ether 314 derived from D-xylose in nine steps... 

M. Yoshikawa, N. Murakami, Y. Yokokawa, Y. Inoue, Y. Kuroda, andI. Kitagawa, Stereoselective conversion of D-glucuronolactone into pseudo-sugar, synthesis of /escudo- -i)-glucopyranose, pseudo-fS-D-glucopyranose and validamine, Tetrahedron, 50 (1994) 9619-9628. 

J. L. Acefia, O. Aijona, R. F. de la Pradilla, J. Plumet, and A. Viso, A Stereodivergent access to naturally occuring aminocarbasugars from phenylsulfonyl-7-oxabicyclo[2.2.1]heptane derivatives. Total synthesis of pentaTV-O-acetyl-validamine and its Ci and C2 stereomers, J. Org. Chem., 59 (1994) 6419-6424. 

K. Afarinkia and E. Mahmoud, Novel and concise synthesis of 2-epi-validamine, Tetrahedron, 55 (1999) 3129-3140. 

The known 7-e carboxylic acid 506, obtained by the condensation of acrylic acid with furan, was used as a substrate for synthesis of validamine, (510) a component of validamycin antibiotics. The treatment of 506 with hydrogen peroxide in formic acid gave the tricyclic compound 507, which after reduction and hydrolysis afforded cyclitol. Treatment of 508 with 2,2-dimethoxy-propane in the presence of an acid gave a mixture of diisopropylidene derivatives in which compound 509 was predominant. Introduction of an amino group, by way of a tosyl ester and azide displacement, followed by hydrogenation and hydrolysis, completed the synthesis of DL-val-... 

Full details on the synthesis of carba-a- and P-D-glucopyranose and the carba-aminosugar validamine from D-glucurono-6,3-lactone have been reported. (See Vol. 27, p. 216, ref 95 for preliminary work). 

A synthesis of validamine and isomers has been achieved by a stereocontrolled nucleophilic epoxidation of polyhydroxylated cyclohexenyl sulfones obtained from (phoiylsulfonyl)- -oxabicyclo[2.2.1]heptane, itself derived from compound 113. ... 

A synthesis has been reported of (-t-) fortamine hrom die known conduritol derivative 88. The preparation from the known ketolactone 89 of carba-a and - -D-glucopyranose as well as validamine, in which the key step is a stereoselective addition of nitromethane tt> the keto... 

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