Chiral N-phosphonyl imines were found to be efficient electrophiles for reaction with diethylaluminium cyanide, a non-volatile and inexpensive cyanide source. The reaction produced chiral Strecker adducts, a-aminonitriles, in excellent chemical yields (94-98%) and diastereoselectivities (95 : 5 to >99%). This synthesis was confirmed to follow the GAP chemistry (group-assistant-purification chemistry) process, which can avoid traditional chromatography and recrystallization purifications, i.e., the pure chiral a-aminonitriles bearing a chiral N-phosphonyl group can be simply obtained by washing the solid crude products with hexane. The chiral N-phosphonyl auxiliary can be easily cleaved under mildly acidic conditions and quantitatively recycled by a one-time extraction with n-butanol.The development of efficient synthetic methods that combine economic, environmental and green aspects constitutes a great challenge in modern organic chemistry. 1-4 It has been extremely difficult to find general reagents, particularly chiral reagents, to enable organic synthesis to be performed without the use of traditional chromatography or recrystallization purifications. 5 In fact, chemistry with these advantages has not been established thus far. However, this green concept would encourage the synthetic community to search for such reagents and related reaction processes to better serve the academic and pharmaceutical industry with minimized use of energy, materials and manpower. In the past three years, our research group has discovered that several chiral N-phosphonyl and N-phosphinyl imines suit the above purpose, which led to the new concept of GAP chemistry (group-assistant-purification chemistry). 5 After this concept was generated, we examined and re-examined previous chiral N-phosphonyl and N-phosphinyl imine-based asymmetric reactions 5-9 and found that all of these reactions can be conducted via the GAP chemistry process.Two of the above syntheses involve the asymmetric catalytic Strecker reaction. 5 It is well-known that a-aminonitriles are versatile building blocks for the synthesis of a-amino acids, which belong to the most important building blocks in organic and medicinal chemistry due to their use in protein, peptide and peptidomimetic research. 10,11 In addition, a-aminonitriles are
Segmentation of an ultrasound image into functional tissues is of great importance to clinical diagnosis of breast cancer. However, many studies are found to segment only the mass of interest and not all major tissues. Differences and inconsistencies in ultrasound interpretation call for an automated segmentation method to make results operator-independent. Furthermore, manual segmentation of entire three-dimensional (3D) ultrasound volumes is time-consuming, resource-intensive, and clinically impractical. Here, we propose an automated algorithm to segment 3D ultrasound volumes into three major tissue types: cyst/mass, fatty tissue, and fibro-glandular tissue. To test its efficacy and consistency, the proposed automated method was employed on a database of 21 cases of whole breast ultrasound. Experimental results show that our proposed method not only distinguishes fat and non-fat tissues correctly, but performs well in classifying cyst/mass. Comparison of density assessment between the automated method and manual segmentation demonstrates good consistency with an accuracy of 85.7%. Quantitative comparison of corresponding tissue volumes, which uses overlap ratio, gives an average similarity of 74.54%, consistent with values seen in MRI brain segmentations. Thus, our proposed method exhibits great potential as an automated approach to segment 3D whole breast ultrasound volumes into functionally distinct tissues that may help to correct ultrasound speed of sound aberrations and assist in density based prognosis of breast cancer.
A series of α-amino-1,3-dithianes have been synthesized via the asymmetric Umpolung reaction of 2-lithio-1,3-dithianes with chiral N-phosphonyl imines in good chemical yields (up to 82%) and good to excellent diastereoselectivities (>99:1). The addition manner by which chiral N-phosphonyl imines are slowly added into the solution of 2-lithio-1,3-dithiane was found to be crucial for achieving excellent diastereoselectivity. The current synthesis was proven to follow the GAP chemistry (Group-Assistant-Purification chemistry) process which avoids traditional purification techniques of chromatography or recrystallization, i.e., the pure chiral α-amino-1,3-dithianes attached with the chiral N-phosphonyl group were readily obtained by washing the solid crude products with hexane or the mixture of hexane-ethyl acetate.
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