合成路线1

3) The condensation of 2(S)-phthalimido-4-(triphenylmethoxy)butyric acid (XVII) with 2(S)-amino-6,6-dimethoxyhexanoic acid methyl ester (XVIII) by means of BOP in methylene chloride gives the corresponding amide (XIX), which is treated with p-toluenesulfonic acid in methanol to eliminate the trityl group, yielding (XX) with a free hydroxy group. The reaction of (XX) with thioacetic acid by means of triphenylphosphine/diisopropyl azidodicarboxylate in THF affords the thioacetate (XXI), which is cyclized with sodium methoxide in methanol as before, giving the protected pyridothiazepinone (XXII). Finally, this compound is deprotected with hydrazine in methanol to afford the previously reported intermediate (VI). 4) The intermediates 2(S)-phthalimido-4-(triphenylmethoxy)butyric acid (XVII) and 2(S)-amino-6,6-dimethoxyhexanoic acid methyl ester (XVIII) have been obtained as follows: 4a) The condensation of L-homoserine (XXIII) with phthalimide-N-carboxylic acid ethyl ester (XXIV) by means of Na2CO3 in water gives 4-hydroxy-2(S)-phthalimidobutyric acid (XXV), which is then treated with trityl chloride and triethylamine in chloroform to yield intermediate (XVII). 4b) The condensation of 6-hydroxy-L-norleucine (XVI) with phthalimide (XXIV) as before gives 6-hydroxy-2(S)-phthalimidohexanoic acid (XXVI), which is esterified with methyl iodide/Cs2CO3 in DMF to yield the methyl ester (XXVII). The oxidation of (XXVII) with oxalyl chloride in dichloromethane affords aldehyde (XXVIII), which is treated with trimethyl orthoformate/p-toluenesulfonic acid to give the dimethylketal (XXIX). Finally, this compound is deprotected with hydrazine in methanol, yielding intermediate (XVIII).