Wiswesser line notation, also referred to as WLN, invented by William J. Wiswesser in 1949, was the first line notation capable of precisely describing complex molecules. It was the basis of ICI Ltd's CROSSBOW database system developed in the late 1960s. WLN allowed for indexing the Chemical Structure Index (CSI) at the Institute for Scientific Information (ISI). It was also the tool used to develop the CAOCI (Commercially Available Organic Chemical Intermediates) database, the datafile from which Accelrys' (successor to MDL) ACD file was developed. WLN is still being extensively used by BARK Information Services. Descriptions of how to encode molecules as WLN have been published in several books. Examples
1H : methane 2H : ethane 3H : propane 1Y : isobutane 1X : neopentane Q1 : methanol 1R : toluene 1V1 : acetone 2O2 : diethyl ether 1VR : acetophenone ZR CVQ : 3-aminobenzoic acid QVYZ1R : phenylalanine QX2&2&2 : 3-ethyl 3-pentanol QVY3&1VQ : 2-propylbutanedioic acid L66J BMR& DSWQ IN1&1 : 6-dimethylamino-4-phenylamino-naphthalene-2-sulfonic acid  QVR BG CG DG EG FG : pentachlorobenzoic acid
^ Wiswesser, William J. (1951). Simplified chemical coding for automatic sorting and printing machinery. Willson Products Inc., Reading, PA. ^ Wiswesser, William J. (1952). "The Wiswesser line formula notation". Chem. Eng. News. 30: 3525-3526. doi:10.1021/cen-v030n034.p3523. ^ Wiswesser, William J. (1968). "107 years of line-formula notations (1861-1968)". Journal of Chemical Documentation. 8 (3): 146-150. doi:10.1021/c160030a007. ^ Wiswesser, William J. (1982). "How the WLN began in 1949 and how it might be in 1999". J. Chem. Inf. Comput. Sci. 22 (2): 88–93. doi:10.1021/ci00034a005. ^ Wiswesser, William J. (1985). "Historic development of chemical line notation". J. Chem. Inf. Comput. Sci. 25 (3): 258-263. doi:10.1021/ci00047a023. ^ Wiswesser, William J. (1954). A line-formula chemical notation. Thomas Y. Cromwell Co., New York, NY. ^ Smith, Elbert George; Addelston, Aaron; Wiswesser, William J. (1968). The Wiswesser line-formula chemical notation. McGraw-Hill Book Co., New York, NY. ^ Smith, Elbert George; Baker, P. A. (1975). The Wisswesser Line-Formula Chemical Notation (WLN). Chemical Information Management Inc., Cherry Hill, NJ. ^ Apodaca, Rich (July 20, 2007). "Everything Old is New Again - Wiswesser Line Notation (WLN)". Retrieved 2018-03-09. ^ Dalke, Andrew (October 15, 2003). "WLN – History of Chemical Nomenclature". Retrieved 2006-12-17.
http://www.emolecules.com/doc/cheminformatics-101.htm Everything Old is New Again: Wiswesser Line Notation (WLN)
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