102(P28) ^1H-^<29>Si PFG-HMBC法の応用によるシリル基結合位置の決定(ポスター発表の部)

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Many silyl ethers have been used to protect for the hydroxyl group. Positions of silyl groups have been determined by indirect methods e.g. acetylation. We demonstrated the application of ^1H-^<29>Si-PFG(Pulsed Field Gradient)-HMBC (Heteronuclear Multiple-Bonds Correlation) spectroscopy to determine the positions of silyl group with accuracy. We used the pulse sequence of ^1H-^<29>Si-PFG-HMBC without low pass J filter as follows: ^1H(1/2π)-Δ-^<29>Si(1/2π) - 1/2t_1-G1-^1H(π) -G2-1/2t_1-^<29>Si(1/2π) -G3 -Acq(t_2). Used PFG ratio are G1:G2:G3 = 2.52:2.52:1.00 and maximum strength is 37.75G/cm. Z-axis gradients are applied in 0.5-1.2msec (typically 1.0msec) duration with sine-bell shaped amplitude profile. Δ is duration time optimized for 1/2^nJ. ^1H-^<29>Si-PFG-HMBC spectra for several silyl ether compounds including silylated anhydroerythromycin derivative (5) and lasalocid A methyl ester derivative (6) were obtained within 30 minutes in high quality. Position of silyl groups were determined by long-range correlation through three-bond coupling (^3J H-C-O-Si=ca 3Hz) based on the ^1H-NMR assignments of oxygenated methine and/or methylene protons. To enhannce the sensitivity, we applied selective HMBC technique, which was recently reported by A. Bax et al, and obtained a good result for the model compound of 1,3-polypol (7). Obtained results strongly indicated that ^1H-^<29>Si-PFG-HMBC technique is suitable and useful for determination of silyl group positions with high efficiency and accuracy.
天然有機化合物討論会の論文
1996-09-02

102(P28) ^1H-^<29>Si PFG-HMBC法の応用によるシリル基結合位置の決定(ポスター発表の部)

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