SynthesisandBiologicalEvaluationofMenthol-BasedDerivatives asInhibitorsofPlasminogenActivatorInhibitor-1(PAI-1) Bin Ye,* Shawn Bauer, Brad O. Buckman, Ameen Ghannam, Brian D. Griedel, Seock-Kyu Khim, Wheeseong Lee, Karna L. Sacchi, Kenneth J. Shaw, Amy Liang, Qingyu Wu and Zuchun Zhao* Discovery Research, Berlex Biosciences, 2600 Hilltop Drive, PO Box 4099, Richmond, CA 94804-0099, USA Received 3 January 2003; accepted 24 April 2003 Abstract—Compound 1 was identified by high throughput screening as a novel PAI-1 inhibitor. Optimization of the B and C-seg- ments of 1 resulted in a series of structurally simplified compounds with improved potency. The synthesis and SAR data of these compounds are presented here. # 2003 Elsevier Ltd. All rights reserved. Plasminogen activator inhibitor-1 (PAI-1) is a naturally occurring serine protease inhibitor, or serpin, that rapidly inhibits the activity of several proteases, includ- ing tissue plasminogen activator (tPA) and urokinase- type plasminogen activator (uPA), by forming equimo- lar, irreversible complexes that are internalized and degraded. 1 PAI-1 plays a major role in preventing fibri- nolysis by decreasing the activity of tPA and/or uPA, and consequently, the level of plasminogen converted to plasmin. 2 Plasmin is an enzyme critical to the lysis of fibrin clots and works by cleaving fibrin to small soluble products. 3 Clinically, PAI-1 is considered to be a thrombotic risk factor. 4 Elevated levels of PAI-1 have been described to correlate with an increased risk of deep vein thrombosis, 5 atherosclerosis, 6 unstable angina and myocardial infraction. 1,4 In addition, elevated levels of PAI-1 are also associated with a poor prognosis in cancer patients, 7 and PAI-1 is believed to play a role in angiogenesis, 8 cancer invasion, 8 and metastasis. 9 Thus, inhibition of PAI-1 would be expected to be of ther- apeutic benefit in a variety of cardiovascular and cancer diseases. To date, several PAI-1 inhibitors including antibodies, 10 peptides, 11 and small molecules 1,12 have been reported. To develop small molecule PAI-1 inhibitors for the treatment of thrombosis, we established a protein-based PAI-1 assay. 13 High throughput screening of our compound library led to the identification of the lead compound 1 with an IC 50 value of 1.4 mM. The lead 1 has a unique chemical structure, good potency, and moderate oral bioavailability. However, its complex chemical structure and poor aqueous solubility render it suboptimal as a drug candidate. Thus, an effort was made to simplify the structure and to improve the potency as well as the pharmacokinetic profile. Structu- rally, compound 1 can be divided into three segments designated as A, B, and C (Fig. 1). Optimization of the B and C-segments using a combined medicinal and combinatorial chemistry approach is detailed in this paper. We started the optimization with the modification of the B-segment (Table 1). The synthesis of the series in Table 1 is exemplified by Scheme 1. Amidation of ()-men- thoxyacetyl chloride 2 with 4-nitrobenzylamine 3 under basic conditions afforded 4 in quantitative yield. Hydrogenation of 4, followed by reductive-amination with commercially available Psoromic acid 6, afforded compound 1 in 78% yield over two steps. The rest of analogues were prepared in a similar manner using dif- ferent amines. Compared with 1, shortening the B-seg- 0960-894X/$ - see front matter # 2003 Elsevier Ltd. All rights reserved. doi:10.1016/S0960-894X(03)00686-3 Bioorganic & Medicinal Chemistry Letters 13 (2003) 3361–3365 Figure1. Lead compound 1 from library. *Corresponding author. Tel.: +1-510-669-4211; fax: +1-510-669- 4310; e-mail: bin_ye@berlex.com