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Validoxylamin A 361 R

Validoxylamin B 362 R Validamycin A 365 R Validamycin B 367 R Validamycin E 368 R

Compounds 361-368 (Part B)

The same group also reported a total synthesis of 6"-ep;'-validamycin A 366 and its diastereomer in which the racemic cyclohexene epoxide 363 was used for condensation with the protected ยก-d-glucopyranosyl validamine derivative 364. The oxirane 363 has also been used to prepare a dl-6'-epi-validoxylamine analog [195,196]. These workers extended their previous work to prepare a dl-2-deoxyval-idoxylamine B analog [197] and to report the first total synthesis of validamycin A via glycosylation of a partially protected validoxylamine A with an a-d-glucopyra-nosyl chloride [198].

Total syntheses of ( + )-validamycin B (compound 367) [199,200], ( + )-valida-mycin A (365) [201,202], validoxylamine B (362) [200], ( + )-validoxylamine A (361) and (+)-validamycin E (compound 368) [202] have also been reported by the same group. In another report, cleavage of the imino bonds of validoxylamine A derivatives with V-bromosuccinimide was demonstrated. This method reports the preparation of synthetically useful derivatives of (+)-validamine and valienamine [203].

The same group has also reported the syntheses of (+)-validoxylamine G [204], (+)-validamycins C, D, and F [35], and ( + )-validamycin H [36] by standard gly-cosylation procedures.

Asano et al. [205] used a combination of enzymatic and chemical reactions to synthesize eight possible mono-^-d-glucosides of validoxylamine A. In another synthesis by Ogawa and coworkers [206], treatment of validoxylamine A or its per-O-benzylated derivative with NBS under different conditions resulted in the formation of mixtures of keto- and aminocyclitol derivatives (e.g., 369 and 370). These compounds were used to prepare the dimeric aminocyclitol 371, which is a potent trehalose inhibitor (compounds 369-371 ).

369 370 371

369 370 371

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