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Thirty compounds that are precursors, analogs, derivatives, or fragments of strigol were prepared and tested for their activity as witchweed [Striga asiatica(L.) Kuntze] seed-germination stimulators. Five compounds showed significant stimulatory activity. Among these were 5-ethoxy-3-methyl-2(5H)-furanone, 3-hydroxy-2,6,6-trimethylcyclohex-1-ene-1-carboxaldehyde, a two-ring analog of strigol, and two isomers of a three-ring analog. Several of the other 25 compounds showed slight and/or non-reproducible activity when dimethylsulfoxide was used as the carrier at 0.1% (v/v) in aqueous solutions. Compounds with such diverse structures as trimethylcyclohexenes, furanones, and bicycloheptenones were among those that possessed some stimulatory activity.

The chemistry of the hydroxymethyl phosphonium salts and their derivatives is reviewed, with major emphasis on reactions in which the quaternary structure of the phosphonium salts is preserved.The subject matter covered in this review is restricted to phosphonium salts that are of interest to textile chemists as flame retardants for cotton. Formally, these compounds are derived from tetramethylphosphonium chloride, Me4PCl, or its equivalent (CH3)4P'Cl-, by substituting a single OR, NR2, or halogen substituent, where R = H, alkyl, aryl, acyl, alkoxycarbonyl, or aminocarbonyl group or combination thereof, for a hydrogen atom in each and every methyl group, or by substituting another anion for the chloride anion. There are many phosphonium salts that do not fall into this classification. For these, the reader should consult a textbook on organo-4 Names of companies or commercial products are given solely for the purpose of providing specific information. Their mention does not imply recommendation or endorsement by the U.S. Department of Agriculture over others not mentioned.