methyl 2,4-anhydro-3-azido-5-O-benzyl-3-deoxy-D-arabinonate 生成 methyl (2S,3R,4S)-3-[[(2S,3R,4S)-3-[[(2S,3R,4S)-3-[[(2S,3R,4S)-3-[[(2S,3R,4S)-3-[[(2S,3R,4S)-3-azido-4-(phenylmethoxymethyl)oxetane-2-carbonyl]amino]-4-(phenylmethoxymethyl)oxetane-2-carbonyl]amino]-4-(phenylmethoxymethyl)oxetane-2-carbonyl]amino]-4-(phenylmethoxymethyl)oxetane-2-carbonyl]amino]-4-(phenylmethoxymethyl)oxetane-2-carbonyl]amino]-4-(phenylmethoxymethyl)oxetane-2-carboxylate