合成路线1

Selective N-protection of sisomicin (I) with HONB-pNz (prepared in situ by reaction of N-hydroxy-5-norbornene-2,3-dicarboximide [HONB] with p-nitrobenzylchloroformate [pNzCl] and Et3N in THF) by means of zn(OAc)2 in MeOH/CH2Cl2 gives 6’-pNz-sisomicin (II), which is selectively protected at the glycosidyl amino groups with HONB-Boc (prepared by reacting HONB with Boc2O and Et3N in THF) by means of zn(OAc)2 and Et3N in MeOH/THF to yield 6’-pNz-2’,3-diBoc-sisomicin (III). Protection of the remaining amino groups of compound (III) with HONB-Fmoc (prepared by reacting HONB with Fmoc-Cl by means of NMM in THF) and Boc2O in the presence of NMM in THF provides 6’-pNz-2’,3,3’’-triBoc-1-Fmoc-sisomicin (IV), which is selectively deprotected by removing the Fmoc-group by means of N(CH2CH2NH2)3 in CH2Cl2 to afford 6’-pNz-2’,3,3’’-triBoc-sisomicin (V). Condensation of protected sisomicin (V) with N-Boc-4- amino-2(S)-hydroxybutyric acid (VI) [prepared by N-protection of 4-amino-2(S)-hydroxybutyric acid (VII) with Boc2O and K2CO3 in diox-ane/H2O] in the presence of HONB and EDC in DMF generates 6’-pNz-2’,3,3’’-triBoc-1-(N-Boc-4-amino-2(S)-hydroxybutyryl)sisomicin (VIII). Basic hydrolysis of the 6’-pNz group of compound (VIII) by means of NaOH and Na2S2O4 in EtOH/H2O at 70 °C results in 2’,3,3’’-triBoc-1-(N-Boc-4-amino-2(S)-hydroxybutryl)sisomicin (IX), which then undergoes reductive alkylation with tert-butyldimethylsilyloxy acetaldehyde (X) in the presence of silica-supported cyanoboro -hydride (Si-CBH) in MeOH at 100 °C (microwave) to give the 6’-[2-(tert-butyldimethylsilyl oxy)ethyl]sisomicin derivative (XI). Finally, compound (IX) is completely deprotected by means of TFA in CH2Cl2 .