1. Introduction of Letrozole
Letrozole is one kind of white to off-whitecrystalline powder. The IUPAC Name of this chemical is 4-[(4-cyanophenyl)-(1,2,4-triazol-1-yl)methyl]benzonitrile. Letrozole belongs to Anti-Cancer;Pharmaceutical material and intermeidates;Active Pharmaceutical Ingredients;Letrozole;Antineoplastic;All Inhibitors;anti-neoplastic;Inhibitors;Intermediates & Fine Chemicals;Pharmaceuticals;API's;APIs;Antibiotics;Aromatics;Heterocycles. 

Besides, its Classification Code is Antineoplastic; Antineoplastic agents; Aromatase Inhibitors; Enzyme inhibitors. In addition, Letrozole is freely soluble in dichloromethane, slightly soluble in ethanol, and practically insoluble in water.

2. Properties of Letrozole
Physical properties about Letrozole are:
(1)Molecular Weight: 285.30274 g/mol; (2)Molecular Formula: C₁₇H₁₁N₅; (3)XLogP3-AA: 2.7; (4)H-Bond Donor: 0; (5)H-Bond Acceptor: 4.

3. Structure Descriptors of Letrozole
(1)InChI: InChI=1S/C17H11N5/c18-9-13-1-5-15(6-2-13)17(22-12-20-11-21-22)16-7-3-14(10-19)4-8-16/h1-8,11-12,17H
(2)InChIKey: HPJKCIUCZWXJDR-UHFFFAOYSA-N
(3)Canonical SMILES: C1=CC(=CC=C1C#N)C(C2=CC=C(C=C2)C#N)N3C=NC=N3
(4)Smiles: n1(C(c2ccc(cc2)C#N)c2ccc(cc2)C#N)ncnc1

4. Uses of Letrozole
Letrozole (INN, trade name Femara) is an oral non-steroidal aromatase inhibitor that has been introduced for the adjuvant treatment of hormonally-responsive breast cancer. Letrozole is approved by the United States Food and Drug Administration (FDA) for the treatment of local or metastatic breast cancer that is hormone receptor positive or has an unknown receptor status in postmenopausal women. Side effects include signs and symptoms of hypoestrogenism. There is concern that long term use may lead to osteoporosis, which is why prescriptions of Letrozole are often accompanied by prescriptions of osteoporosis-fighting medications such as bisphosphonates.

Estrogens are produced by the conversion of androgens through the activity of the aromatase enzyme. Letrozole blocks production of estrogens in this way by competitive, reversible binding to the heme of its cytochrome P450 unit. The action is specific, and letrozole does not reduce production of mineralo- or corticosteroids. In contrast, the antiestrogenic action of tamoxifen, the major medical therapy prior to the arrival of aromatase inhibitors, is due to its interfering with the estrogen receptor, rather than inhibiting estrogen production.